You get a nicer, significantly simpler interface. You don’t need any tricks. You don’t have to google how to work yourself out of a bad state, ever. And you get near-perfect git compatibility (ie you can use jj on a shared git repo, doing all the same things, and your teammates won’t know the difference).
I’ve wondered if there is a psychological thing here: someone who spent time memorizing all the git nonsense may have some pride in that (which is earned, certainly), that introduces some mental friction in walking away???
I don't think it's just mental friction. Suppose you've learned git well enough that everything you do in it is automatic and fast, and the things which aren't fast by default you've built aliases and tooling for over the years. Yes, starting from ground zero you might want something like jj, but at the current point in your life you're not starting from ground zero. Switching to jj means learning another tool to achieve similar outcomes on your workflows.