Even if we set aside any potential spiritual, or child-rearing value. Marriage is a very important institution in helping people achieve economic mobility, it increases your household income significantly, as well as seriously reducing your cost of living. Anecdotally, my cost of living was drastically reduced when my girlfriend and I moved in together (thereby splitting a 1BR), however given that we aren't married we individually have to save a good amount of money in cash accounts in case of a breakup. If we were married, we could reduce our cash savings by 50% and instead invest that money into the open market. Moreover, we would be far more likely to take care of the other financially if one went to school if we were married. Marriage, and the commitment it entails changes the attitudes of individuals towards each other by ensuring that we can plan for a combined future. all that exists outside of societally constructed benefits like joint taxation and healthcare.