The Argentine tango did not originate in brothels. And really, the theme of prostitution and sex work would make for a dreadfully boring romantic partner dance: there's very little courtship, flirtation, suspense, give and take (beyond the haggling)... Just pass the cash and get on with it! Romantic dances symbolize mutual pleasure and passion. In prostitution, things are rather unequal and motivations are rarely mutual. If authenticity and the avoidance of the squick is what we're going for here, a romantic dance simulating prostitution would fail both ideals.
The tango, like any other form of music adapted from folk origins, is music about life and all its varieties, not just romance.