I think what makes swingers swingers is that we take sex much less seriously than everyone else and are not (usually) territorial about our potential or current sex partners. Even vanilla people who hook up and have casual sex still seem to be upset at the idea that their latest fuckbuddy is also fucking someone else. They SAY this person means nothing to them beyond friendship and sex, but deep down they want them all to themselves, at least for now.
I know people who have fucked hundreds of people in the vanilla world but still treat each partner like it's a mini-marriage, even if it's just for the night and I know swingers who have only played a few times but each one was simply a fun experience and nothing more - they aren't jealous of whom their fuckbuddy has fucked the day before or the day after.

