You get to play in my campaign isn't enough?
Seriously ... what you get is a game that's more than just a beer and pretzel's anything goes game. That doesn't matter to everyone but it's not the type of game I run. If playing a specific race is more important the playing a cohesive world that has history, distinct cultures and so on then I may not be the DM for you. See also my note on working on RP desires, I'll do my best work with the player to get the "feel" of a race if not the mechanical implementation.
Well, that and if I don't like the campaign world, it will affect the entire campaign. To reiterate: if the DM ain't happy ain't nobody happy. If the world doesn't come to life for me, I don't see how I can make it come to life for my players.