Yes. For many reasons. The biggest summary of these reasons are that for all other purposes, we acknowledge that a 14 year old is not mentally capable of making adult decisions, of reasoning as an adult (driving a car, drinking alcohol/smoking tobacco, signing a legal contract).
But the bigger reason is that when we try a 14 year old as an adult, for violent crimes, we are patting ourselves on the back because, oh boy, we protected ourselves from the evil 14 year old. When all we did is put this person in jail for some ridiculous amount of time, only ensuring if and when they come out of the prison system they will be a violent criminal.
I never said that the law was rational.