If parents can't provide the guidance needed during that time, then I hope there are other adults around helping teach these kids how to adult. It is a VERY difficult time of life, and to be released into the world with no help seems cruel.
My ex was weird with his kids when they turned 18. He went from being the epitome of an authoritarian parent (I shit you not, his 16 year old still had to ask if he could have juice with dinner instead of water - which I felt was completely excessive as far as parenting goes) to being like, "Okay you're 18, you can do whatever you want now."
It did not turn out well. There is a slow transition of power that must start early in life. I believe that children are people from the time they're babies (crazy, maybe, but there it is). I believe that children have likes and dislikes and that they are no less valid than my own. So if they don't like a certain food, I don't make them eat it. If they prefer to have a bath before story time instead of the reverse, I try to accommodate it. Especially with tasks that are hurting no one by changing up.
So then when there were important decisions that had to be made, they knew I would do everything in my power to accommodate their preferences. It didn't always work out, but they certainly responded much better to me, knowing that I was doing my best to incorporate their wishes.
Sorry, I went off topic there, but yes the religious element is so much more gross. controlling a child (especially a daughter) with religion and then hoping to get her married off to a man who will also control her is just gross. And the very definition of the patriarchy. Let's not let women find their own way, as we allow boys, but rather, let's teach them to be subservient to the parent and then to the spouse. Ew.