In a sense the quest for the emancipation of black people in the U.S. has always been a quest for economic liberation which means to a certain extent that the rise of black middle class would be inevitable.
It's not really like you have a thing like a supermodel anymore. It's more of a word than a real existence. I think, also, looking at it from a designer's point of view, at one point maybe they felt the stars took too much attention away from the clothes.