While there's many reasons why people get sexually involved with another person, and particularly strangers they've just recently met. But usually it's stemmed out of mutual chemistry, sexual attraction or affection. Not to open a can of worms, but how many times has anyone had sex with someone for reasons other than these typical ones, RE: ' Revenge, pity, loneliness, horniness, etc.
Hell, I'm pretty sure that I have including having sex just for the hell and fun of it. We behave like we can only have sex under certain conditions and situations and, well, that's all well and good - but they aren't the only reasons to have sex - just the approved ones. I've had sex with men and women just because I'm bored and I don't have anything better to do - then again, I've never been "prudish" about having sex and someone once called me the poster child for promiscuity and I laughed and said that I was okay with that... because I love sex and I love to have sex and you don't get to do it all that often if you keep playing by the rules our social norms have established. The trick of it, of course, is not being stupid about it and knowing when to accept one of those other reasons and when to just say no and walk away. Chemistry is one of the most misunderstood things and especially when people expect chemistry to just happen - and then get miffed or are unhappy that the "click" wasn't there; they don't understand that you can create chemistry with someone by engaging them in meaningful conversation but, nope, I learned that I don't need chemistry and not much in the way of being attracted and if it's pure lust, well, that works but our social norms insist that lust is not a good reason to have sex with someone. And, to me, there is no such things as empty or meaningless sex... but, then again, I've never played by those stupid social rules...
My wife had a lot of sex in college our of pure horniness. In her 30's, she was propositioned by several younger men in their 20's. With my permission, she had sex with a couple of those young men out of curiosity about how it would feel to be the "older woman" for them.
She enjoyed the attention, but the young men were not very experienced so the sex wasn't that great. She had one amazing "date" with a 60+ year old man from Russia, and the sex was remarkable.
I'd had sex with two different individuals, a man and a woman at the request of my present wife. I would place them both within the "pity sex" category. Both of them were long time friends of my wife long before I met her. The woman had been widowed for a number of years and hadn't had sex for a very long time. One evening after dinner with my wife she asked me if I would be willing to help her friend out and have sex with her one-on-one? I was caught off guard and didn't know what to say. She went on to tell me with whom as I replied..."She's pretty good looking", why sex with me? My wife tells me that she's always wanted to use a strap-on with a man having had discussions with my wife that she pegs me all the time and had asked my wife if she could have me for an evening. I reply: "Really, you're OK with that"? Yes, she was so about a week later I met this woman at her house, and we had some really wild sex together that night to which I had to tell all to my wife afterwards. The guy had been divorced for 10 years and still not in any relationship. My wife and I had him over for dinner one evening and had a movie for the three of us to enjoy after dinner. After dinner we made our way to the family room to watch the movie with my wife sitting between the two of us on the couch. Well, my wife says to me that she'd been talking with him about his curiosity about getting a blowjob from another guy and had heard that men are really good at sucking dick. I reply to him: "You wanting a blowjob from me"? He says he'd love to get one as it's been over ten years since anyone has sucked on his cock and had never received one from another guy and your wife told me you love to suck dick. I proceeded to suck him off right there with my wife sitting next to him. Afterwards we watched a three-hour movie and at the end of the movie my wife and I sucked him off together. He left a very happy man as my wife, and I made our way up to our bedroom to enjoy some great sex together.