I guess I am thinking of retired folks, widows and widowers and such, marrying. We all know there is no way they are going to have kids. I just feel like the “procreation” argument sort of shuts them out.
Marriage is based on the reproductive model. The key word is model. That doesn't mean a couple has to reproduce. It means that the activity in which a married couple engages could lead to reproduction. (I'm trying to put it politely. I don't want to use raw terms. But, let me put it this way: Certain parts are meant to go into certain places.)