Exactly, societies do not exist without marriage law, whether it is tribal law, or a state religion's law, or government law, or whatever, the society has to have marriage laws.
Why we are wasting time pretending that we are going to get the GOP to start campaigning (and winning) on erasing marriage and divorce law in America, removing marriage from the public space entirely, is ridiculous.
Saying it's ridiculous doesn't make it so. The state already deals with what was formerly the domain of marriage and divorce laws (i.e. custody and property distribution) without a marriage or divorce ever having taken place.