And its wrong. I was talking about how the law treats people once they become 18. Am not saying parents should be 100% responsible for their kids but that the law and society need to acknowledge that people under 20 still have a lot to learn and are still teens by definiton (which is someone who is between 13-19).
As for the "bad situations". People under 20 living in bad situations is not excuse to have high expectations from someone who has not reached their 20s yet. Also there are people who are under 18 who live in bad situations yet i dont think you would like to lower the age of majority to 13 or 14 right? And its not all kids who live like that, some kids are living fine lives. And if a kid is being mistreated by its parents then the law needs to take their kid away from them, not make the kid a legal adult.
"Experience has no substitute", thats not what I meant. Am talking about the fact that someone who is 18 or 19 is still to young to be treated like old man, also someone who is 18 or 19 is still in college. And i brought up WW2 because thats where Americans decided to lower the age of majority, so they could drag people into war, which as a consequence caused the modern youth to not develop themselves properly. And as you stated some people who where 14 also participated in the war. If americans saw 14 year olds participating in war in those times they would of lowered the age of majority to 14 just based on mere observations rather than psychological development. And I dont think you would feel comfortable with that right?
If the age of majority was 20 (like it used to be in Japan) teens would have better time to develop. And dont even get me started on how the law criminalizes people who are either in highschool or first starting college as "grown ass folk": https://www.bostonglobe.com/2020/02/28/opinion/18-year-old-offenders-belong-juvenile-not-adult-justice-system/