[quote=@Shorticus]
<Snipped quote by NuttsnBolts>
Mongolians/Native Americans = Vikings!? India = Vikings!?
[/quote]

The less people know about history and the people who lived in it, the more all fantasy will gravitate towards one of the two RenFaire singularities. Anything that is strongly medieval and/or tribal with iron age+ technology will immediately be Vikingised as soon as boats are mentioned. Anything that is vaguely steampunk or late medieval high-tech will immediately become Piratised whenever they reach a coastline. Those are the typical settings that people with no knowledge (and therefore no basis for a middle ground) of the society that these people are living in will jump to because it makes them feel like they know what they're doing and that they can worldbuild too. This is (slightly) more avoidable if you remove the notion that these are fantasy counterpart cultures and write out long, detailed descriptions of the cultures, but you're bound to get TL;DRs and people who assume and appropriate anyway. 

Of course, this could also be attributed to ignorance of a much more innocent kind, where the player is afraid to write about certain cultures because they're afraid of making an offensive stereotype and don't know what aspects of this culture are and aren't politically correct to bring about. People are a lot more comfortable being vikings, because they're white and it's much more forgiving to mistranslate those cultures, and they're afraid of other kinds of characters because nobody likes to come off as ignorant/bigotted. It's a completely logical fear, and there's not really an easy solution.

It could be mostly cruel stupidity or misguided reverence, however optimistic you feel. Or maybe something different, it all depends on individuals, but this is what I've seen with this kind of thing.