The state has the right to protect marriage which, after all, involves the joining of estates and concerns the rearing of children. The marriage license is intended to certifying that each party is free to marry, that no other person has claim to either party. There's an old saying: "the road to hell is paved with good intentions" That may be an overstatement, but it makes the point.
Most government programs (e.g. social security) are started with good intentions, but their merit is better judged by their consequences. Marriages licenses are wrong because they require men and women to get state permission to marry, which is presumptuous. The proper way to deal with fraudulent marriages is to punish offenders severely (e.g. large fines) when they record the marriages.
As a matter of fact one does not have to have a license to "marry" since two persons who cohabit for a period of time are married in a sense. The license is merely a first step toward formalization of that relationship and is in effect a declaration by the two parties that neither is already married.