I can't speak for everyone but I want to say it was valuable for me to be separated from my family at that age and put in another semi-structured environment like college. My family was incredibly supportive, well-roundeded, upper-middle-class, and therefore I lived in a neighbourhood surrounded mostly by other families from my background. Being able to be separated from that environment and exposed to a diverse background of wealth/privilege was incredibly helpful to my capacity for empathy and willingness to be wrong. (I went to a state college in a primarily working class city.)

What does this have to do with college? You can just move out.

College provided me with a semi-structured environment that gave me set obligations (classes, activities) without the pressure of finding and managing employment (while also being exposed to others who did have this pressure, which again, did so much for acknowledging my privileges in background).

Colleges also often provide a space for people to access mental healthcare for the first time independently without the overwhelm of psychologytoday.com or other directory. Please note that there are several significant and life-altering mental illnesses that also typically kick in around this time, and early intervention does wonders.

It's not the years (roughly speaking) -- move college to 16, or 20, the point still stands. For many people it's the first time they leave the only family/friend/schooling setting they've ever lived with.

Some people certainly don't need that, but I think a soft-entry into the real world in a more limited environment is not to be dismissed outright. It was certainly helpful for me.

No matter how good your family and secondary schooling is (and for many people, it is lousy!), I think that having only one environment and set of perspectives before you're assumed to be a solo capable adult is not ideal.

What does this have to do with college? You can just move out.