That's Game of Thrones, which is firmly rooted in medieval fantasy, and that garb is absolutely legit. You historical purists amuse the hell out of me.
There's that whole "us vs. normal people" dichotomy again.
Joe Blow who's only exposure to clothing not from the past few decades is having seen two of the Lord of the Rings movies and three episodes of The Tudors can't tell that the garb and armor on HBO's GoT is a smorgasbord of badly-recreated and podged-together crap from 1000 BC through 1850 AD.
We, belonging to a society of people who get together to swordfight with fake weapons and do historical research and read fantasy novels and base our garb and armor off of such sources really should be able to tell, and a lot of us can.
Sure, we could keep lowering our standard for what's "good enough" every time a new "fantasy" TV show comes out where the director told Costuming, "No, I want them in something tight, like those things the dancing girls wore in the saloons, whattayacall 'em, corests? And make sure our male lead is in something recognizably modern-ish and Western, so the audience can tell him apart from the bad guys". We could also try to do the best we can and not let (ignorant) popular culture decide our standards for us.
In the end, I suppose it's up to us as a society.