I hope some people who have casual one-night stands chime in on this topic, as I'm genuinely curious. To be honest, I feel like a big part of what makes sex so intimate for me is knowing that we're sharing something with each other that we wouldn't be sharing with just anyone. It's not even the sex so much as just being naked with each other when we wouldn't do that with other people. Like just a short while ago my husband and I were taking a nap snuggled up next to each other in the nude. It felt so personal feeling just having his bare skin against mine. Is it still as personal or intimate when you've shared the experience with so many different people?
“This planet has - or rather had - a problem, which was this: most of the people living on it were unhappy for pretty much of the time. Many solutions were suggested for this problem, but most of these were largely concerned with the movement of small green pieces of paper, which was odd because on the whole it wasn't the small green pieces of paper that were unhappy.” ― Douglas Adams, The Hitchhiker's Guide to the Galaxy