The question that I sometimes get is, Why do we have state issued marriage licenses; and why do you as a minister of the gospel have to abide by a state issued marriage license?
First, it is fraud to solemnize a wedding ceremony without the expressed authority of the state (that means without a marriage license).
Second, America and its government has been built on biblical principles and that includes recognizing marriage as the foundational institution of society. Marriage produces citizens. The state must recognize a marriage because it has sought to reward marriage for providing it’s society a stable reproducing society. That is why there are state issued marriage licenses. So they can record marriages. The state also recognizes the value of clergy and churches to its society and has welcomed clergy to use their marriage licenses rather than keep the ceremony a secular transaction as they do in other countries.
Third, not having a registered marriage certificate in a state courthouse could become a liability if several years down the line a couple decides they are “divorcing” and discover they have no legal recourse in divorce court because there is no registered marriage certificate. Or, as one case I am familiar with, if at the time of death the deceased’s estate gets contested in the courts by adult children over the inheritance going to the remaining “spouse” and not to them.