I've never paid for sex, but I've been to plenty of strip clubs in my youth, and I have to agree with your sentiment. I always thought - "man this is for losers - what's the point?". If you have to pay for it, you're lame.
marriage has been put in place by most cultures at some point for one reason or another. religious, control, and quite often financial. "you marry our daughter and promise to feed and house her and we'll give you a dowery" and sometimes the merging of families and their businesses.