The states invented them as a way to dictate who could and could not get married for the purpose of making sure blacks, whites, Asians and Indians didn’t mix.
https://mattwilson32.wordpress.com/2015/06/30/the-ugly-history-of-the-marriage-license-in-america/
What is LICENSE?
In the law of contracts. A permission, accorded by a competent authority, conferring the right to do some act which without such authorization would be illegal, or would be a trespass or a tort.