Everyone would be so good-looking and emotionally functional that sex, love, and intimacy wouldn't be tainted by capitalism. But in the real world, people age. People get fat.
People get themselves all fucked up in car wrecks, industrial accidents, and bad marriages.
And so there exists an entire class of poor unfortunates who couldn't get laid if their sad, hideous lives depended on it. For these folks, orgasms don't come cheap. There are also some relatively attractive people who simply enjoy paying for sex. Lucky for the aesthetically challenged and the seriously twisted, a whole class of shrewd capitalists earn their bread by closing their eyes, plugging their noses, and pretending they are somewhere else. We're talkin' 'bout the bad girls.