In 2 Timothy 3:16 it says, "All scripture is breathed by God and profitable for teaching, for reproof, for correction, and for training in righousness."
The first reasons I'll be looking at, is for teaching, and training in righoutness. As Christians, we are to teach others as we see in Matthew 28:19. Now, of course this seems almost impossible for girls, as we can't teach men. But this doesn't mean that we can't teach. I know for a fact that, especially in larger congregations, they are always looking for people to teach Bible classes. Now there are some congregations that may only have one, or no children's classes because of how small they are. I have been in places like that. But even so, there are still several opportunities to teach, and we need to be prepared for those times. Especially for in the future. Most teen girls grow up and have children. It's just a fact. And we need to be prepared for that. Ezekiel 33:6, "But if the watchmen sees the sword coming and does not blow the trumpet, so that the people are not warned, and the sword comes and takes any one of them, that person is taken away with his iniquity, but his blood I will require at the watchman's hand." I know it seems forever in the future, but no matter how many times you read the Bible, if you pay attention to it, you will always learn something new. :)