That's why religions tend to assign child rearing a extentential "Go straight to hell" punishment if you don't do it. It turns out it's a great way to keep your religion around.

Although many religions encourage the raising of families more than secular culture does, I have not really seen this "have kids or go to hell" thing you're describing.

They don't want you to sleep around, and in some religions they don't want you to use birth control, but there's not a lot actively saying you need to have kids.

Sometimes having children is strongly implied for those who follow the path of marriage (and may officially even be the purpose of that), but there are typically also paths where people are expected to remain celibate.

Arguably, say in the Catholic church, there is too much emphasis on the latter, what with celibate clergy and everything. In LDS I would say family is more of an ideal. This extends even into the theology. Catholics say "'til death do us part", but LDS say husband and wife go to heaven together and stay married there forever. Hinduism overall seems less obsessed with correct behavior (it has dharma, of course, but no simple hell thing), but it also provides both householder and ascetic paths.

I think religions sort of take it for granted that enough people will want to get married, and that if you get married you'll have kids. Instead they're worried about self control.

Little did they anticipate that the superego would maintain its iron grip without help, that the rationally-planning ego would have the means and motive to skip kids entirely, and that the id would get so distracted with hatred of other people that it wouldn't even try to bring them together, even in unwise or destructive ways. But that's where we are.