I’m 65 and would happily take a hit for the team. I just retired from 30 years as a family doctor, and I see how people just start progressively losing their mental edge after 70. Not absolutely every single one, but most folks.
An alternative would be a test every voter takes to be able to vote. DMV-like 30-question multiple choice purely on facts of civics and current events. I don’t see that happening given the history of poll tests in our country.
Brain maturation (fronto-cortical pruning) is not complete until 26 years of age.
Ever notice how you can work at 16, vote and be drafted/enlist at 18, drink at 21 but can’t rent a car without a co-signer until 26?
Now you know why. Car rental agencies don’t study human neurophysiology, but they damn well know there’s a difference between people who rent their cars before and after 26.