we USED to have common law marriage when the frontier was open and recording was difficult.
When recording was “voluntary” it was rife with fraud. Consider divorce. Divorce is because you say you are divorced and there is no obligation to childsupport or even standing to subpoena for testing. It is a leftists wet dream.
We still have common law marriage in many states in America, Texas for instance (and with no license),
With common law marriage you can call yourself married, but for it to be legal, you have to do it in a state that recognizes it, and meet the legal requirements of that state.
Making your relationship “legal” is a personal choice, just at it was 20 or 50 years ago.