[josephg]

I think we can all guess how that came about. Back in the day there was no contraception and the church was at the center of community life. Imagine the inconvenience and heartbreak to everyone involved from unwanted pregnancies! Especially those from teenagers, who I'm sure were pressured into suddenly abandoning their own ambitions to become unwitting parents. Pre birth control of course church leaders would council people to simply say no to pre-marital sex. Sure it'd be difficult for some, but I'm sure avoiding any unwanted pregnancies was worth it for everyone involved, and better for the community at large.

Fast forward a few centuries and that (very practical) advice has become 'word of god' moralistic. Now with modern birth control we have better ways to avoid pregnancy than abstinence. But (unsurprisingly) the church's practical advice hasn't caught up with modern technology.