Do you really think that people don’t want their marriage to be legal?
No one makes people seek to make their marriage legal, they could have followed your advice in 1950 or 1850 or 2010, or 1810, no one cares if you don’t legalize your marriage, but normal people don’t want to live like that.
For instance, in the military you are just a single person, unless you show them that you are legally married to someone.
Would you want to be in the military with a wife and a few kids, and them not be recognized as your family?
What about the ending of marriages?
No, I’m not saying that people shouldn’t make their marriages legal. I am saying that they should do the extra step of seeing the Justice of the Peace when they pick up the marriage license from the courthouse the law already stipulates that they get.
You currently have a situation where ordained ministers act in place of civil officials and wield authority held by the state. Think of that authority as a Trojan Horse brought within the Church’s gates.