Marriages have always been “recognized” as legally binding, which means “by the state”. That way inheritance, protection of children, and so on are legal.
The ridiculous idea that marriages should just be private “contracts” with no public or legal ramification is a standard libertarian pie in the sky utopian “if human nature was all different, everything would be all different”.
Libertarian schools of thought differ over the degree to which the state should be reduced. Anarchists advocate complete elimination of the state. Minarchists advocate a state which is limited to protecting its citizens from aggression, theft, breach of contract, and fraud. Some libertarians go further, such as by supporting minimal public assistance for the poor. Additionally, some schools are supportive of private property rights in the ownership of unappropriated land and natural resources while others reject such private ownership and often support common ownership instead.
Another distinction can be made among libertarians who support private ownership and co-operative ownership of the means of production; the former generally supporting a capitalist economy, the latter a libertarian socialist economic system. In some parts of the world, the term "libertarianism" is synonymous with anarchism.