Treatment will help prevent further crimes and still give the juvenile time to really understand what they did wrong and why it is not okay. They should not be completely off the hook of any penalty, but the sentence should be more focused on treating and rehabilitating than punishing them.
Unfortunately, treatment alone often won't fix juvenile crime in a given individual. Punishment is absolutely required in certain cases. The fact that we go for treatment first and wait for it to fail proves that punishment should be the main solution. However, it never hurts to mix in a balance of treatment and punishment on a case by case basis.