You are wrong on so many levels. First, most couples get married without regard to whether they can have children together (nowdays, not always true in the past however).
Most people assume by default they have the physical ability to "have children together" unless they learn otherwise, so that statement would be rather supercilious.
At least as many as there are people who assume by default that they "can't jump off a skyscraper and fly"... unless they learn they were actually born on Krypton.
In fact, while about 10-15% may not be raising children by the time they are in their 40s, many more of those who are raising children are not raising the biological children of the two who are married. Many more people are choosing to not have children with each other, including taking permanent measures to avoid children.
Others such as myself and my husband are going out of our way to not have more kids.
Thank you for sharing.
I'm sure that individuals throughout history have attempted to put limits on the quantity of children they have, and didn't attempt to "be fruitful and multiply" to the same degree as... hamsters. Contraceptive measures are as old as Onan. What else is new?
Second, you do not need to be married to have children. Many people are not married when they have children.
Outside of rare anomalies, such as in vitro fertilization, or virgin births - one needs to be in an intimate union with another in order to beget children - whether formally recognized as marriage, informal cohabitation sometimes recognized as a "common law" marriage, or a union which only lasted 1 night.
Obviously specific laws, formalities, are culturally specific variants on the general anthropological rite of marriage or unions.
Like mentioned above, many married couples are not raising their own children together, but rather normally the child/children of one from a previous relationship.
That's merely consequential, given that if something hadn't occurred which resulted in the dissolution of the previous relationship, they would be in that position to begin with.
Marriage benefits society regardless of whether kids are involved or the level of "intimacy" the couple has.
Yeah, I'm sure that Tina and Ike's union benefitted society... or Rihanna and Chris Brown's - united as fist and face.
It allows society to have a designated person to legally make decisions for their spouse who has greater authority than anyone else. It places someone in a position to take at least some financial responsibility for that person, especially for final arrangements and/or final medical costs. Marriage makes people happier and healthier, regardless of whether they have children or not.
Those would be legally-specific minutia relating to the greater anthropological issue - given that unions which tend to naturally result in children, and ideally greater intimacy than say, two male buddies - those legal minutia are ideally contingent on the hope that the couple in question would have some mutual degree of intimacy and accountability to each other to begin with.
Since obviously a wife-beating spouse who is creating medical costs by putting his wife in the hospital, rather than aiding her with them.
But anyway, given that you admitted above that you have children, it seems somewhat futile to be concerned about anomalies and exceptions anyway, such as couples who are married but never beget children - given that they don't apply to you, or to most.