My POV comes from the publishing world. As Erasure and American Fiction point out, "Black" has to do with marketing. Editors are thinking about the market segment called Black readers. And for a while, book publishers equated the Black experience with the urban experience. Or with the ghetto or criminal experience. E.G., pimps, prostitutes, pathological behavior.

The thing is, there are many kinds of Black experience. Unfortunately, if a publisher sees that an author is African American, he can't just be a writer. They have to see him as a "Black writer" in order to align him with their idea of what they think will sell.

Anyway, Erasure and American Fiction really have fun showing this conundrum for what it is.