Probably because it's not officially announced yet. Netflix released their schedule and it's on there, people start talking, and the show runner confirmed it. But an actual official announcement with a press release from Netflix + Frederator + Konami hasn't happened and it probably wasn't meant to be revealed just yet. I'd imagine the announcement will come with a trailer or at the very least a few stills, but that's total speculation on my part. Aside from seeing the old concept art and then some of the updated stuff ~7 months ago, I have no idea how far along it is. I was shocked to see it's a 2017 show, didn't realize it was that far into production.
Edit: Looks like Netflix has made an official statement now but still no screens or a trailer. Hm.
Cheers for that final update. At least it's been officially confirmed and announced by Netflix, which is a start. Can you - or anyone that is keeping tabs - please keep us posted here if screens do show up?
Like I said before, I'm really curious to find out what kind of art style and tone they ended up going with. Imagine they'd actually do a more or less serious and sombre show with lots of Gothic imagery, Lords of Shadows style dramatic narration (centering around family, heritage and corruption) and plenty of hommages to classic Universal and Hammer horror monsters, just like the oldest games were/had. That would be incredible.
That said, I'd give it a chance as long as it is not another show full of memes, edgy humor and oversimplified character designs. Nothing against shows like Adventure Time, Gravity Falls, Rick & Morty or Bob's Burgers, to name a few, but for a Castlevania adaptation I want something more in line with The Last Unicorn meets Vampire Hunter D, i.e. melancholy, drama and gothic adventuring interspersed with bad-ass action. I guess my expectations might be a bit too high now that I think about it...