When the fathers of a bride and groom perform a wedding service, must they also be registered by a state?
At the end of the day, the state really only cares about your offspring. If two people want to shack up, the state doesn't care one iota. But if and when they're open to a legitimate issue, the state desires to certify their union and assigning each child a serial number, etc.
Other than accounting for offspring, governments traditionally couldn't care less about the "institution" of marriage.
Thus, like your beer, perhaps your civil marriage license will expire in the near future. Then you'll have to re-up (or not ) just like the Army.