it's not that it's just better for the kink..it just avoids complications. your girl isn't falling for a stranger. a person who is a friend poses some weird issues or at least can. that's why usually it is just teasing or exhibition unless you full on swing.I’d take a stranger over Terrence. I hate games where the friend bangs the girlfriend. If it’s with friends, it should be just exhibitionism , stranger stuff fits better for that kink