Good grief. Willful ignornace. The "society" in this case is the state that grants the license. That is the body that creates the rules under which this contract is maintained. The state can't supervise ALL contracts and are not OPMNIPRESENT. Not a profound point. But in the case of marriage, they very well do supervise this one. That is what civil marriage is! I have no idea why you guys want to expand the govt to get it into every other conceivable kind of relationship - primarily to make those in the relationships FEEL GOOD. That is Leviathan.
The state is involved in civil marriage because that is the context in which people make babies. And we have decided, to avoid complete societal chaos, to make some rules about that.