Yes, I realize that but regardless, an 18 year old is likely to be more mature than a 14/15/16 year old when it comes to driving. They have more experience in life. It doesn't mean no 18 year old is going to make bad choices when driving.
But when you look at the statistics, older drivers (as in early 20s) are much safer than teenagers.
Not all minors (as in under 21) are considered juveniles. Most states legally define juveniles as 18, while some define it 16 and 17.
Obviously, you and I don't agree and won't agree. So, maybe we should just agree to disagree.
They do that already, it's called your permit. There's no way to judge someone's maturity.