It's why there's a difference between military school and regular schooling, too.
People who are aware of their own strengths and weaknesses aren't "immature" in my opinion, either. I think it would be much more immature to join the military because other people wanted you to or you wanted college money, only to end up going AWOL or something. A friend of mine got a dishonorable discharge from the military at a young age for something similar.
I know myself and I know what I'm good at and where I don't belong.