For purely financial reasons, if you have a substantial career, are able to do well on your own, and children aren't in the mix, I understand your point of view. I never wanted kids and I waited until I was 50 to get married. Both of us had good jobs and had built up equity which we were able to combine to create a life that neither one of us would be able to afford separately.
That said, it's the intangible emotional support I get from my wife and her family, as well as the knowledge that we can share financial resources without legal roadblocks or a tax penalty that make it a plus for us. Of course you have to marry the right person as well as uphold your end. That's the truly tricky part.