All that is understood.
Urban fiction publishers are getting their work on the shelves because they, for whatever reason, are good promoters.
"Literary" writers aren't promoted well and never have been, black or white. Major publishers will generally promote authors who are already celebrities. That's just how it is. If a literary author doesn't also know how to promote their work on their own, then their books will be the ones with the spines facing out, and the street fiction will have the cover facing out.
It would be nice if the best artists were also the most business savvy, but unfortunately, that's not always how it works in the book world.
All that is stuff I am learning on my own, as an aspiring writer, as well as from the "Making of a Best Seller" yahoogroup, which you can join here:
themakingofabestseller-subscribe@yahoogroups.com