Scientifically, it has been shown that the human brain, specifically the prefrontal cortex, is not fully developed till 25. This can lead to teens making impulsive decisions without thoroughly weighing in the consequences. Adult brains are wired to notice errors in decision-making better, but a teenager wouldn't notice any error. When the age of majority was set at 18, we did not know about the human brain like we do now. If brains of people under 25 don't have foresight, why not set the age of majority at 25? At least it's makes more sense.
If a person under 25 does not feel responsible enough to move out, he/she can stay with parents as long as he/she wants.
Some people need to break free. They do better on their own, and they need to get out of their parent's home.
As for driving, it must be learned. It is easier to learn something while you are still partially in "learning mode" than to learn it as an older adult. Their brains are TOO developed to learn something new and not be bad. This is true for the piano and language skills as well.
Brains under 25 do have foresight. Many people married as young as 16 and are happily married years later. And they have proven themselves to be capable because many are living on their own without support from their parents. Do we really want to take away control and responsibility away from people who already don't have any?