Seriously, what's wrong with you guys?
It's a throwback to Victorian sensibilities.
During the industrial revolution, when poverty and high society became more aware of each other and there was more friction between them, the Victorians (also Christian) did all they could to codify and 'standardise' how people should behave or think. Basically they wanted to normalise everything (which is an evolutionary drive, in their defence).
There were horrific, widely-read pamphlets about how:
> nudity is abhorrent and manners were the most important thing
> never talk about sex, it's taboo
> always be prim and proper in behaviour - manners and politeness (read: not talking about stuff) is paramount
> a woman should do everything for her man and be totally monogamous (there's a bit about it
here and it ties directly to this topic)
> nudity in any way is totally taboo (see: full-body swimsuits and swim-dresses for women from the time)
> violence was the realm of 'men' and isn't a taboo (though women shouldn't talk about such things)
(I can find evidence of this, but all my reading/resources are from about 3 years ago when I studied it at university, so it would take some time.)
Basically, in all modern media, we are still chained in a subtle way to these old sensibilities (in my opinion, this is informed conjecture). The origins of Hollywood still inform the tropes and patterns of modern mainstream cinema. Same goes for mainstream games, which are far earlier in their development. Hollywood broke out of the violence stuff in the '60s, and literature broke out of
everything in the 1910s. Games also require the catalyst of violence as an action-marker/gameplay mechanic, which is fair enough.
TL;DR: from the Industrial Revolution (the codification of Christian, ie Victorian, sensibilities), nudity/sex was marked as a taboo topic of discussion. Violence, however, has
never been marked as a taboo topic of discussion.
It's not so much a question of "in games", it's a question of "in Walmart". There's loads of games dealing with sexually explicit subject matter, they are just rarely widely distributed.
This is true, I've taken the topic as being focused only on AAA-games, as they are most in the public eye.