Why do a lot of people ociate music genres with race?

Well, its easy to do with the way the media stereotypes music for certain races. I personally catch a rap song I like once every decade or so. Very rare. On the other hand, I hate country music, which people expect me to like since I am an older white Southerner. I prefer old Rock, which is expected, and that includes Jimi Hendrix and Chuck Berry. I must admit that several black friends have surprised me with their love of groups like Phil Collins, Queen and The Doors.