Actually, your stated experience is completely in line with my thoughts: It is rational to get married with the expectation of children. My wife and I were married 7 years before our first was born for precisely the same reason you "didn't want to have kids." That is, I was still in school. I concur with you that everyone should have a sustaining relationship. Where we differ (perhaps) is that our shared value that everyone deserves such a relationship necessarily means that everyone should have the right to marry. I see "marriage" and "committed relationship" as two distinct things (Aside: I am supported by the evidence in this as roughly 1/2 of all marriages end in divorce. It immediately follows that 1/2 of all marriages have nothing at all to do with sustaining relationships). At least until this new type of marriage was defined, I think I can say without objection that going into a marriage you know, intellectually, that you've only got a 1 in 2 shot at having it last. Given the enormous personal toll, financial toll and legal toll a divorce entails, that's quite a risk. So, for the couple with no expectation of children, I cannot see why they would assume it. The tax advantages are negligble. The end-of-life, inheritance and similar concerns can be achieved with relatively painless boiler plate Durable POA documents and wills. Sure, there's outlier benefits like pension plans that only pay a spouse survivor benefits, but those are few and far between and the last of a dying breed. Further, for at least 1/2 of those entering such a relationship, the inevitable termination of the relationship would be greatly simplified and far less painful financially and otherwise. Which is easier? Tearing up a couple of POA documents and editing a couple of wills? Or a divorce?
So, marry in the absence of intent or desire for children? Why bother?
When I said I wasn't sure if I'd have asked my wife to marry me if I knew she were sterile, some took that to the fantastically inaccurate conclusion that I was saying I wasn't sure if I'd have wanted to spend my life with her. Of course I would have. But that does not mean (or require!) that we wed. That Marriage != committed relationship in the presence of marriage's failure rate is obvious to all but the most myopic of minds.