Once again you steer the conversation around to this red herring: it is not about infertility.
People who are involuntarily infertile can be married.
The issue is impotence: the inability to perform the unitive act.
I know of a case where a couple in their 70’s (I suppose, possibly older) were living together to reduce expenses. They didn’t marry because they were each collecting Social Security and the woman would have her benefits cut if she remarried.
I see. It was about money.
They were visited by the priest and told that they were ‘living in sin’ and causing a scandal. He insisted that they should marry.
He insisted that two people who were only living under the same roof as part of a crass business deal should get married? I highly doubt it.
Would the whole story be that they were, in addition to pooling their cash, physically intimate?
There was no question of procreation.
And procreation isn't really germane to the discussion.
Why should they marry?
If they were having a physical relationship, then St. Paul has an answer.
Why should they even be allowed to marry?
Because those who are unimpeded from marriage and who wish to live together as a married couple have a moral right to be married.
You seem to think the purpose of marriage is only about sex and nothing more and that true love and spiritual connection can only be achieved through intercourse.
I may not have a lot of experience in this field but I would hope love is deeper than that and just being able to be in the presence of my wife would spiritually fulfill me.