It's spelled Filipino, actually. Phillipines is the nation, Filipino the nationality.
In short, that's not a "fact". That's what you believe because of the culture you come from. There is no objective human cultural context for clothes; this fact is shown by the tribes of people who wear nothing at all. What clothes are considered appropriate or not is entirely driven by what culture they come from, and this is largely determined, if you go back far enough, from the climate that culture originated in. Warm climate, few clothes. Cold climate, many clothes. It's really as simple as that... and European cultures such as ours are cold-weather cultures at their core.
The issue that this raises, then, is which cultural context a game supposedly set in the past should set itself in. Most do the easy thing and use our present culture as a basis, just slightly modified to fit the different technology level. This is why most videogame characters in games set in the "past" or worlds based on our past think and act like people of today: It is what the market expects. It's also much easier to do that than to try to create something that is a truly believable and internally consistent fantasy world which understands the history of the actual time period from our history it is inspired by, considers the changes to that culture that it is making -- magic, greater women's rights, whatever -- and then implements them evenly and properly. Instead of doing this, two major things are done:
-First, costume designs are designed to appeal to the modern-day fanbase of the game (or anime, movie, etc) and have nothing to do with believability (of what people from that place may have actually worn if the place were real), the plausibility of using that costume in combat, or anything else.
-Second, people act like the people of today and do not think the way people of the time would have thought. Humans in the past had the exact same level of intelligence as we do now -- they are humans too, they were just as smart as we are -- but they had a much lower level of knowledge about the world than we do, and their viewpoints on the world and reality were very different from ours. We can't fully understand how they thought, but we can try. It is very hard to do this, however, and the harder you try the more you confuse your audience. As a result, this issue, applying modern-day values to people in the past, is really the greatest issue that the fantasy genre does, should face, but does not. It is very easy to do this, really, even when trying not to. Most designers don't even begin to try (and most audiences probably don't want them to).
Game designers always have to deal with these two issues in fantasy games. Perfect "accuracy" to the real world (with magic) might not be good, of course -- if you want stronger roles for female characters in your game than most major nations had at the time, for instance, greater alterations are necessary. Doing things like that is often good. I'm definitely not saying that they must have perfect accuracy to the real world or something like that. I just want a world that is believable and makes sense -- where the rules that are there seem to actually fit. These conflicting impulses can be managed... just look at Hibiki (LB2) or Nakoruru (SS series). Rimururu too, though I like her SSIII/IV costume better than her SSV and beyond costume. Good character designs, great characters. While it is in a stupid way entertaining, you don't need panty shots every ten seconds (as the Soul series does) and ridiculous costumes to make a good female fighting game character... Samurai Shodown does have Mina, of course, but that's just one character, not a broad trend. Those characters also do a relatively credible job of realistic attitude too, though of course modern influences cannot be avoided. But maybe those benefit from being largely set in Japan (and with a largely Japanese cast), which a Japanese development team will understand better. I mean, in SS1, set in the mid 1700s, one of the stages is somehow set in San Francisco which is somehow part of the USA at the time... and there's that American Ninja character... um, yeah. Right.

(they can certainly do it if they want. It just comes off as silly.)
The Soul series, in both of those categories, definitively leans towards the "forget believability" and "forget history" approaches, for the most part, though bits of actual history are mixed in. The people act like modern people, not 1500s ones (as with virtually all fantasy outside of novels). And the costumes look like modern fantasies, not ones people of the time might have worn. This applies to every character in the game pretty much equally. How they think, though... every character does have an impressively deep backstory. It's one of the great things about the series, really. Some things make no sense, of course (Sophitia and Cassandra believing in the ancient Greek (Olympian) Gods, for instance), but other things work. The good fantasy book serieses are far better of course, but outside of that, the Soul series is probably about as good as anything in characterizations.
I can't help but wonder how these people keep managing to travel all over the world so many times in such short periods of time, though... :lol
Anyway, Talim. Talim's Filipino. The Phillipines are in Southeast Asia, a very warm (and wet) part of the world. In that part of the world, before European contact people generally didn't wear much clothes on account of the heat. Clothing originated as a response to cold, after all. In places where it was less cold, people wore less, until Europeans arrived and started forcing them to wear more. So what would pre-1500s Filipino women have worn? Likely as not, just a skirt with nothing above the waist (and probably no underwear under the skirt either, though that's pretty much a universal thing... loincloths existed worldwide from very early on (usually worn more by men than women), but the modern-style underwear all Soul Calibur characters wear (sans elastic I would hope, but modern)? That's a modern invention, weird as that certainly seems.). In Thailand and Cambodia for instance women did often wear tops, but they were just small wrap-type things. Though Talim's shirt is looser than those would be and also covers her shoulders, it clearly comes from that concept (and hopefully from Phillipine sources, I don't know). Obviously they could no more do toplessness in a modern game and try to get away with that T rating in the US than they could put in full dismemberment (when you hit someone with a sword, they come apart...) and expect to get on Japanese shelves.
Perhaps even more importantly, however, audiences don't really want realistic fantasy worlds. People best understand the culture they are in. So, say, take your average fantasy RPG. It does not reflect Medieval culture. If it did, people would have major problems understanding it. Many people simply would not be able to understand a culture where modern materialism simply did not apply, where to most people concerns about whether a thing (such as an idea, scientific discovery, or a technological improvement) was religiously permissible mattered more than whether it would improve people's lives or increase human knowledge... though really, I think a game set in classical Greek Sparta, that actually tried to represent actual Spartan culture of the time, could be very interesting. For instance, why isn't there a great Peloponnesian War game (reality based or with fantasy elements)? I love fantasy, and Medieval fantasy (fantasy is probably my favorite genre in general in fact), but it'd be pretty great to see a bit more variety of settings.
And no, something like Castlevania which randomly mixes Ancient Greek, Medieval, Renaissance, Modern, and other elements all together doesn't count.
Anyway, so we get the costumes that we have, in games like Soul Calibur, conglomerates inspired by various times and places that wouldn't quite fit in any of them, but are supposed to look cool anyway. In Talim's case, at least in Soul Calibur II and Soul Calibur III, the results were good... she got costumes that looked like something that would fit a people in Southeast Asia (reasonable for a warm climate), while also being something the games' target audience will like.
I can't defend the degree of transparency in her pants, though. While there certainly were some semi-transparent fabrics there, would they really be THAT transparent? Seems doubtful... but I don't know for sure.
There was one character in an early '90s fighting game who was this Polynesian boy who actually did just wear a little grass skirt/loincloth thing just hung down in the front and didn't cover anything else... but it was a 2d game, so you couldn't exactly often see anything. It was interesting, though, that it was actually a character from a culture like that put in a culturally acturate costume... that is very rare.
Many other Soul Calibur characters come off much worse, though. It's not just the female characters. I mean, look at Rock. Without steroids (and modern fitness techniques), did people actually get that big? Not often, if ever! Then there's Taki, who has a fairly ridiculous bodysuit. And Cassandra and Sophitia worship the Olympian Gods, a good thousand years after the last people stopped believing in them. Plus, they wear some Ancient Greek style costumes, something that needless to say was also over a millenium out of date (and then Cassandra has that one with just a shirt, underwear or something, and thigh-high boots...). Sophitia also lost her chest armor in her first revision, something which I pointed out no warrior would ever do. While protective garments worn during combat varied from place to place (From 15th century full-plate armor to naked, partially blue painted Pictish warriors), in each game Sophitia's costume made less and less sense and protected her less and less. Why in the world would someone wear leg and arm armor but not chest armor? Well, we know the answer, fanservice, but there's certainly no logical one. Logially, a female warrior would most likely wear something a lot like the male warriors of her society wore, just adapted for a female body... but that'd cover up far too much skin to satisfy the fanbase, so that's out from the beginning.
Oh yeah, Xianghua... her "chinese dress" costume, for instance? That style of clothing was introduced to most of China by the Manchu dynasty after they conquered China in the 1600s. Even then, they did not reach that form-fitting shape until the late 19th or early 20th centuries. There's absolutely no history behind a Chinese character in the 1500s wearing something inspired by that kind of clothes. I don't know if any of her costumes have much of any historical believability, really... cool designs, but not believable. Oh well.
Or consider the two new anime-artist-designed characters, who fight in high heels (both pretty much impossible and not worn in those parts of the world at the time).
Compared to that stuff Talim's costume seems sensible, really, though the fact that the transparency was obviously done purely for fanservice reasons and not for any kind of accuracy does negate that to a large degree.
Really, why can't there be games with the kind of incredible, believable design of fantasy book serieses like The Lord of the Rings, A Song of Ice and Fire, The Sword of Truth, or The Wheel of Time? With very few exceptions, games on that level just do not exist, and it's too bad.