Your name is fitting. You've got some real meatball logic right there and have the nerve to think you are mentally qualified enough to even be involved in a discussion of the hypocrisy of our juvenile justice system. Let me apply your "logic" to the police - They work and pay taxes so they should go to jail for life when they kill too. Whats to stop a cop from killing everything in sight if he has no consequences once he becomes a police officer?
The difference is the context. Society loooks at the young kid and says hey, he might not be an adult but he has so many options. He could go to school, get a job, etc. but instead he's wasting his unlimited potential to be a killer. Might as well lock him up forever now. They look at the cop who kills and they say, oh he's a cop he must have had no other option but to kill. Might as well kill that scumbag w/o a judge trial jury or proper investigation because anyone dangerous to a cop is definitely dangerous to everyone. But the truth is there is no absolute right or wrong, especially when we dont know the circumstances beyond kid kills cop.
As long as it's not a capital offense like murder, these kids just keep popping in and out until they either commit a capital crime and get tried as adults, or turn 18 and keep committing petty crimes and join the adults in prison. There is no magical age which makes you responsible. If they truly felt that kids werent responsible until 18 they'd arrest their parents. Outrageous some would say, but they already do that in the civil justice system. If I have financial damages incurred through the actions of a minor, who gets sued? The parents. What if the kid is 17 years and 355 days old on the day it happened? Parents still get sued. What if the kid steals millions or destroys a company? PARENTS still get sued.