Are we talking music or life?
There's a NY bias in American media in general, which includes but isn't limited to hip hop. Most of the major corporations are headquartered there, the major networks, the major sports leagues, etc. Historically non-East Coast rappers had to hustle a little harder for notoriety than East Coast guys did...
Alot of that has changed in the social media era, you're no longer dependent on NY or NY labels/A&R's to get on. But I think there's still truth in it...
As far as life in general, I think it's a "big city" bias in general. NYers, Chicagoans, Angelenos, Atlantans, etc all tend to feel superior to people from smaller cities. That's just a life thing...