Really? Jazz was voiced by one of the greatest legends of all time, Scatman Crothers. There is a reason why he sounded like an urban black...because he was voiced by an urban black man.
I don't know about Blaster and Buster Jones, but Buster has played some black characters as well.
Plus, you know BOTH OF THEIR HISTORY FIT WITH THEIR VOICES.
And aside from the voice, I don't remember Crothers' Jazz being all that "urban" anyway. He had kind of a cool way about him, but he wasn't a walking caricature like the movie version.