And people can't do all that without government? Why not?
Because in our country marriage is recognized by the government which confers special priveledges and legal benefits to those couples that may or may not be obtained by unmarried couples.
Recognized by the government or not, Marriage is the joining of one man and one woman.
That the government seeks to encourage marriage, through providing married couples a lower tax liability is irrelevant to those who demand to alter that which defines marriage, as a means to help them find the legitimacy intrinsic to marriage, which exists because of the very standards that they seek to remove, thus stripping it of legitimacy.
Open marriage to same gender unions, then by your own reasoning, marriage must be opened to siblings, Mothers and son, Dads and daughters, more than two people, varying species... and by allowing all of that sick shit to "be Married" the state 'legitimizes' or normalizes that nonsense... effectively ending marriage, and the culture whose viability rests upon the principled standards that define it.
Reasonable people recognize
that, as NONSENSE!