Back in the Sixties we were all given the mantra, "old enough to fight, but not old enough to vote?" It seemed to make sense, until you realized that being old enough to hold a gun and shoot when ordered doesn't entail the maturity to decide what should be shot.
But in those days maturity itself was under attack.
I'd like to see that pesky constitution returned to more of its original form, mainly by repealing every amendment that includes the clause "Congress shall have power", etc.
Congress had plenty of power to start with.
You may like the New York Times quote, mentioned here.
**While “old enough to fight, old enough to vote” was one of the catch-phrases of the 1960s, the sentiment behind it had been expressed decades earlier during both World War II and the Korean War. But for many years there was opposition to lowering the voting age, including from The New York Times, which repeatedly argued against it. “The requirements for a good soldier and for a good voter are not the same,” said a 1967 Times editorial. “For the soldier, youthful enthusiasm and physical endurance are of primary importance; for the voter, maturity of judgment far outweighs other qualifications.”