You’re not a developed adult at 18. Here’s what happened
The right to vote in the USA has always been tied to age (and to race, and to gender, and sometimes to land ownership and perhaps some other bullshit). The age for voting had been 21, but the age for being drafted into the military to die in Vietnam was 18, so a lot of citizens protested the dubious war in Vietnam (of which deposed former President Richard Nixon declared that we had “achieved peace with honor,” formally crowning himself as The King of Bullshit). So congress lowered the voting age to 18, to try to quell the protesters.
That’s ALL there is to it.
You are not an adult at 18 in any behavioral or cognitive sense.
Women generally are functioning adults by 25. Men, by 40, if ever.
My favorite Mark Twain quote: “When I was 20, I couldn’t believe how stupid my father was. By the time I turned 30, I was very impressed by how much the old man had learned.”
So let’s end the harangue we’ve been having over here about someone who is 18 being an adult. You’re not. You’re just not; but you won’t know it until you are.
https://slate.com/news-and-politics/2013/04/new-york-minimum-smoking-age-why-are-young-people-considered-adults-at-18.html