One of the things that always seems to be missing is one important fact:
"What is the interest of the government in Marriage?"
It used to be that marriage was encouraged and mandated as a means to minimize the abandonment of women and their children by cads. It was an enforced personal responsibility.
But government has done away with personal responsibility by providing support to all comers including women and their children out of wedlock.
So what is the interest of government in this institution?