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???
jj is harder to adopt for people with a thorough mental model of git, because it's harder to accept jj commands at face value. I know it's modifying my git tree, so I feel compelled to grok exactly what it's doing, but that's distracting and time consuming.
People like me should probably trial jj exclusively for two weeks, to shed that antijjotic resistance and form a more clear-headed opinion.