In 1971 the United States Government lowered the minimum voting age from 21 to 18, in response to widespread social unrest.
You see, 18 year olds were being drafted and sent against their will to fight in the Vietnam war.
And a lot of these teenagers were wondering ‘hey, how come you can force me to go fight in a war that I was too young to vote for? If I’m still kid why are you allowed to send me to die in a war?“
So at least in the US, the reason we’re considered adults at 18 is so that we can die as soldiers.
As for if it would affect proship discourse if the age of majority was 21, I can’t begin to guess because the last 50 years would have been very different.
