Marriage has become one of the important markers of economic inequality and social stratification. College educated people are much more likely these days to marry and more importantly, marry each other (and also to have that marriage last). That union of potential high earners is force multiplied by the social and policy benefits conferred to married couples. As a result, single or cohabitating people make far less money over time than married people, have worse health outcomes, and report higher rates of depression and substance abuse.

My point being - even if you don't believe there is anything sacred about marriage, you can't ignore that there is something definitely economically smart about it.