Not everyone who gets married plans to have children, and it is just as easy to procreate outside of marriage as it is inside of it. Limiting marriage only to those who are biologically capable of creating children together would only be logical if one were to also a) illegalize extramarital sex, b) make procreation a requirement for every married couple, and c) illegalize marriage for anyone who, for any reason, is infertile, and dissolve marriages between any couple who does not create a child together. Unless you're prepared to argue just as hard for all of those conditions as well, then you've got to drop the marriage-is-for-the-children assertion, because it's just simply not true.

And that's not resentment speaking at all… it's just logic.