Historically, those with obvious sterility (castrated men, impotent men, women without vaginas) could not get married. In the Catholic church, which still adheres to roman marriage laws, these are absolute impediments to marriage. In fact, permanent impotence is an impediment to marriage in many US states today. A marriage can be undone if the man was found to be impotent before the marriage was contracted, and the impotence is permanent medically.

Here's a Utah law firm offering advice on how to annul your marriage should you have found the man you married to be unable to have sex: https://www.isfma.com/law-and-order/when-ending-a-marriage-o...

Here's a review of case law in BC from the 2000s: https://disinherited.com/family-law-matters/annulment-for-no...

Scientifically, one cannot know if you're sterile until you've tried. There's no 'test' for sterility that truly works or that there hasn't been an exception too. Legally, once a marriage is fully consummated, it's more permanent than if it weren't. Historically, a marriage that was consummated could not be dissolved and was considered permanent at that point, so even if you later found out (usually after many years) that you couldn't have kids, the marriage would continue. Similar to how old people stay married.

I'm giving an historical view on marriage. Not saying how things should be. You seem incredulous at this view, but it was the prevailing view of marriage in Europe and the West for thousands of years.