Well, sometimes we do
(for certain values of "we")
When I got married in the Catholic church, I did have to vow to "accept children lovingly from God" and if we were known to be an infertile couple, we would have needed special permission from the Bishop to get married. It was made clear that we were expected/required to have unprotected sex. It was also made clear by the marriage class instructors that birth control is very much against the rules but nobody expects parents of a kid or two to follow that rule and failure to break that rule leads to more kids than a couple can responsibly raise.
Not missing the ex-church or the ex-wife.
