Quite aside from that, though, I'm still not seeing any reason to assume that relationships in general exhibit this problem - only that it's not quite as uncommon as the highly atypical nature of my own experience led me to surmise.
(Or what I hope to be the highly atypical nature, anyway. If marriages like mine are anything except vanishingly uncommon, that's a serious problem. There are so many improbable circumstances around the way mine started that I've seen no reason to assume many similar relationships exist - but on reflection it occurs to me that I've failed to account for the possibility of stochastic convergence.)
You're not required to have kids.
I guess what I'm trying to figure out is why even start a relationship if you don't get anything out of it. Never mind getting to the point where you start producing kids.
No, but a lot of people want to. (A lot of people have kids without the formality of a relationship, too, but that's a whole 'nother kind of problem.)
I guess I'd say that for most people there are a lot of reasons to want to be in a relationship - good reasons and bad ones alike. With rare exception, nobody goes into a relationship expecting that it won't improve their life in some way, and if you're not seeing what you might get out of one, then I can't see any reason why you should start one.
It seems like a lot of people do eventually discover that they don't get out of a given relationship what they hoped they might, or what they previously did - but that's also a whole 'nother kind of problem, and because it often involves strongly felt responsibilities to people other than oneself, a kind that is rarely easy to solve even if there's no clear way to incrementally improve upon the status quo.
I don't think I've done a very good job explaining it here, but I'm not sure how I might do a better one.