There are scientific studies that prove there is a mind - body connection. For instance, if we smile it actually makes us happier: https://www.scientificamerican.com/a...e-you-happier/ --"A spate of recent studies of botox recipients and others suggests that our emotions are reinforced—perhaps even driven—by their corresponding facial expressions."
And there is no doubt that when my H and I have good sex--I am kinder, more patient, smile more, etc. for a while after--sometimes it can last days (it would have to be really good for the afterglow to last more than 24 hours ) so I think people who just want sex are not getting the most out of life. I find the concept a bit sad (you should at least be caring friends) and if it was more than just an accidental one night stand--someone in that relationship could eventually get hurt.
So it is well known that people do this but IMO these types relationships aren't healthy for us. When I was with someone in a sexual relationship once and he didn't want to commit, I moved on--when he called wanting to see me (I didn't return the call) then showed up at my door one night (I refused to answer because I was in a committed relationship with H)--did it hurt him emotionally? I do not know but he was the one who was unable to commit. I was not going to jeopardize my relationship with H for someone who was seeing others and treated sex so casually. Since that relationship was all about sex it felt wrong to see him anymore. Sex jeopardizes friendships but I don't think that was what this guy was about. Perhaps I am old fashioned?