Government must be involved in marriage.
At the start of this nation, marriage was only recorded in a non-uniform means. church records were not reliable and inconsistent. Additionally people went to the courts to disolve a marriage with only a church record to prove a marriage.
Thus the governement has to have the central role of record keeper. A license is just a recording and a means on making sure those that marry are legally able.
Laws such as inheritance, incompetency, medical surrogacy are all dependent on a consitent and uniform rule of marriage.
Additionally as a society we reward the insitution not the individual. Marriage is about promoting the insititution which proliferates the society for future generations. Homosexuality only proliferates recreational sex.
Thus the governement has to have the central role of record keeper."
If we make a distinction between "marriage" and "legal contracts" then we do not need government to annull a marriage. If we let churches handle the marriages, then records are of little to no importance.
"Laws such as inheritance, incompetency, medical surrogacy are all dependent on a consitent and uniform rule of marriage."
I wrote that "[e]ach couple should have its own contract for its specific circumstances. Some couples already do this via pre-nuptial agreements." I wrote this to address the point that you raise. The purpose of the contract is to legally "form a union for the purpose of shared benefits and legal protections" such as those you cited.
"Additionally as a society we reward the insitution not the individual."
I'm a fan of limited government, rather than a state that engages in social engineering, no matter how well intentioned.