antiRepublicrat: “What business does the government have sanctioning a marriage?”
I can answer that. Government has an interest in encouraging activities that build up society. You may not agree, but marriage is an institution that is very, very beneficial to society at large. If more people would marry and stay married, there would be much less demand for government provided social services, like welfare.
In general terms, this has been used as the reasoning behind the massive government expansion over the last 70 years.