I think @blck37 simply is not attracted enough to pay for sex with some folks. Not everyone wants to hire a twink just like some won't hire a DILF even if he's as hot as Allen Silver or Jim Walker
Some folks dislike tattoos, body hair, certain body types, etc.
I do agree with you that the issue of ethnicity is in a whole different category though. In the early 2000s I contacted someone on Manhunt and told him: I'm usually not attracted to gingers but I think you're very handsome. He automatically blocked me after saying he found my compliment insulting.