> The voting age being 18 was changed in the 70s, primarily so they could more easily justify sending 18 year olds to fight in Vietnam. Prior to 1971 it was kind of agreed that 18 year olds were still basically children.
I think you have it backwards: "They" didn't have any trouble sending 18 year old that couldn't vote to fight in Vietnam. It was those 18 year olds who demanded a greater say in the political process because that was being demanded of them.
https://en.wikipedia.org/wiki/Twenty-sixth_Amendment_to_the_...:
> This means young men could be required to fight and possibly die for their nation in wartime at 18. However, these same citizens could not have a legal say in the government's decision to wage that war until the age of 21. A youth rights movement emerged in response, calling for a similarly reduced voting age. A common slogan of proponents of lowering the voting age stated "Old enough to fight, old enough to vote".
Also, according to that article, there were efforts before 1971 to lower the voting age, they just couldn't pass the very high constitutional amendment bar.