More simply put; government shouldn't enforce morality.
Society got along just fine before governments recognized marriages, when it was just the church that recognized it.
Please name for me when exactly that time was?
Governing authority has ALWAYS recognized marriages, from the dawn of recorded history. There has never been a time, anywhere where it has not been involved with marriage.
In medieval Europe, the Church (in the form of the Roman church) was in charge of marital issues...and family courts, and inhertance cases, and sexual crime, etc. with the POWER (and backing) of the government. Hence the church at that time WAS a governing authority. In Protestantism, as in early colonial America, a similar argangement was found.
Later, slowly but surely, secular governing authorities assumed what church (governing authorities) formerly had administered.
Since marriage involves issues of: private and government benefits, insurance, inheritance, children, custody, adoption, abuse, enforceable divorce, etc., etc., government, in one way or another always has, and should, be involved.
That's why the gay "marriage" issue is so important--and can't be avoided by libertarian fantasies.