A lot of it is US campaign finance laws I think www.sciencedirect.com/science/arti...

Precisely! That's often why places implement hard retirement ages, because it becomes very hard to tell a powerful senior person that they've gotta give it up.

And it's specifically the powerful, why it's a -cracy. Simultaneously everyday old people face unfair agism!

Then there's all the powerful courtiers they have placed around them so they don't have to do the actual work.

Also, this is a traditionally conservative argument, but within a democracy it is dangerous if a non-worker majority can vote itself funding from a laboring minority.

Retirement should be based on WAR not age. (Wins above replacement executive.) Someone doing a bad job doesn't imply their replacement will do better!