How come comics created by people of color don't get as much exposure as the mainstream ones?

Milestone Comics is perhaps one of the few exceptions:

http://en.wikipedia.org/wiki/Milestone_Media

But how come other people-of-color owned and created comics don't get as much notoriety and exposure?

How come you don't hear too much about people oc color working in the comics industry? Or about people-of-color-owned comic book publishers?

I have heard of Jim Lee who works for Marvel/DC.

Please help.