I don't believe there can be much more casual sex than in a marriage. Shit, It becomes so casual it's boring. So what's the big deal? You are attractive ,smart and probably funny as hell with the right dude. If you have ever lived on farm or a ranch, there's a bunch of casual sex going on. The animals certainly seem to enjoy it. Hell, I'm old now, but the best sex ever I had, was what would be called 'casual' sex. Reason ? it's fucking honest.