Ah me! Another guy who thinks that when a naked man and a naked woman have exchanged money alone in a room together there's some sort of Law of the Universe that dictates eveything and anything that happens.
Flash: They make it up as they go along. That's why there are Statutes, Laws, Bylaws, House Rules and individual SOP's (his and hers) to 'help' them stay out of trouble while having their half-hour together. If they're agreeable people, polite, considerate, and there are attractions—of whatever kind—between them, just about anything can happen. Somewhere. Sometime. Absolutely NOT to say that 'everything' will ever happen to you—or me—ever, anywhere.
So why would you imagine all any guy ever gets to do is rub her backside? And how bad can that be, anyway? Think of it this way: you bought a NR, and backside's all you got so a) either she was off (unusual since she's a pro, and customers may come easy, but they aren't all that plentiful) or b) you're off. If all you consistently get is the minimum, better look at putting out more than the minimum. These days, minimum's about $60 bucks, no shower, a bad attitude and clumsy, greedy hands with dirty fingernails. That'll by you just a backside, fer sure. More almost always gets more, but can cost exactly the same.
At least spino you asked a question that could be answered, unlike so many guy's who early on ask: "Why ever would you go to a [SC, MP, insert either one] when you can get FS from an escort [or HJ from MPA] for the same money?" My question to you, standing in for all those guys: Why are you asking? What's it to you? No one asks why you're 'wasting' your money w/ escorts? Who said FS is the only game? Ever thought "different strokes for different folks" mighta been invented to answer the first guy who asked the Q back in cave days? It's a big world. Get out and try something different, instead of trying to match what you imagine w/ your limited experience.
Sorry for the rant, a bit unfair of me to pick on the question behind the question. My advice, read a page or two of Massage Forum posts, go to a place people seem to like, have session with a MPA most guys rate well and then ask, "what's the deal?
Betcha don't ask. Have fun.