Why is the government in the business of marriage at all?

Marriage and a Merger!

Key Points

“Marriage” is a social construct and it seems odd that the government is involved with it in any way.
All the government should care about from a secular perspective is if a person is presenting as an individual or a group for the purposes of commerce, property, and taxes.
As such, the government should create mechanisms for people to group together in any way they see fit, just as companies can merge in any way they want.