People don't want to see the world for what it is; they spend their lives pretending things are otherwise. Prostitution cracks the veneer, its actuality threatens to break the artificial limits our lives already, silently, secretly, and shamefully transcend, but people want to brush such confessions into the corner, under the carpet.
It's strange that for centuries we've happily paid for other humans to exert their bodies for our pleasure, whether it be a postman, a waiter, a boxer or comedian, whatever. We've also a long, long history of having sex for pleasure. Is bringing those two things together and paying for sex such a bad thing?