Why do some people think they have to change who they are and talk a certain way just because they are talking to people of a different race?

I've noticed that some people do that and I think it's just to fit in or they might think it'll make the other person more comfortable and relaxed, in a slightly ignorant way. I don't put on airs, I'm me and talk the way I do to everyone. Though there are times my friends and I would talk certain ways to mess with tourists on the boardwalk. :D That was fun.