The government doesn't belong in the business of marriage. At all. It shouldn't be run by the government.

"But the benefits marriage gives you on taxes etc!"

... is inherently discriminatory against those who don't want to get married.

Maybe the business of divorce should be kept, but that's a matter of "okay did these two or more people live together and do they not want to anymore? Let's figure out how to divide joint assets and manage child visitation."