Years ago I asked one provider I saw (black girl) why she didn't see black guys. She said her neighbors start calling the cops when they see black guys coming in & out of the building all day, but they ignore an endless parade of white guys. This was in the Bx near Southern Blvd & the 180s by the zoo - not a lot of white people live around there, which is ironic in itself.
It's still fucked up, but at least she wasn't doing it because she was racist. She was just a girl trying to do incalls under the radar. That's just one provider's reasoning.