Fear of consequences has always been a necessary part of maintaining law and order. Since the consequences to youth offenders are so light they have no reason to fear them, the natural result is a lot of youth crime.
Of course there are other contributing factors, but none of them change the fact that if serious crimes don't have serious consequences they will continue.
It really is that simple. Human nature is human nature. If you can get free stuff without having to do hard work and there is no practical reason not to, someone is going to steal it.