I'd agree on that from my more Machiavellian perspective, if you can raise kids from birth to be indoctrinated into your faith, why would you forsake that AND open up another avenue in which your most devout members can be corrupted.

Hell even Star Wars showcased this with Anakin, and how every time the possessed bitch attacks the priest their first choice is to try to fuck. Making them able to marry and have kids removes that temptation, grows your numbers and you can focus on promoting family values even more through example.