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???
Also, I dislike all of the alternate git frontends I tried, because they are opinionated in a way they clash with my workflow.
Moreover, I don’t think the git CLI is that bad. Once you learn some basic concepts, it makes a lot of sense and is pretty consistent.
Most problems people report stem from a refusal to learn the underlying structure and models. That is on them. And when using a different frontend, they don’t disappear either. They are just abstracted, to allow you to avoid learning them. But they are still there, and you will probably still need to know them at some point.
It's very easy to fall into the trap of believing this: git's implementation fits together neatly enough that it feels like the best you could do. Like, yes it's complex, but surely that's just intrinsic complexity of the problem? (Also, I think we all sometimes feel like someone with a different view must just not know as much as us.)
But if you have used other version control systems (I'm thinking particularly Mercurial here) you realise that actually some of that complexity is just totally made up by git.