At 25 the brain is no longer plastic enough to learn self regulation. So if you wait till then to give people the chance to make mistakes you end up with a whole lot of women-children who can't function at all. The whole point is that you need to let people make mistakes so they can learn from them while they still can.

Saying that you have to wait to be an adult to make adult decisions is like saying that we shouldn't expose anyone under 3 to language since they can't speak.