It's a LOT easier for a kid to play pickup basketball or football and develop those skills at a young age than it is to find a T-Ball league outside of the suburbs. Inner cities simply aren't equipped to develop the 5 year old kids with the early love of the game, and the basic skills needed to be even prepared for a travel baseball league. I mean, you start travel ball when you are already good enough to start travel ball, you don't just walk on at 12 with no experience playing baseball and hit the ground running...
Every school I ever attended, from elementary through high school, had at least one baseball diamond (with that awful gravel, but y'know...) and the ability to play at recess, but those just don't exist everywhere, so those kids who might have been inclined to check out baseball end up using the basketball hoops drilled into the wall of the school and getting their early skills there.