Getting rid of the fixed keyboard helps a lot (my preferred form factor), but even in the classic laptop form factor is makes a ton of sense IMHO.

There's a lot of small niceties that pile up into a better experience, the sister comments cover a bunch of those, so I'll focus on a macos specific nice point:

iPad and iPhone apps can now get direct touch when running on a laptop, instead of the mouse mode. With this, there is now a perfect platform able to run Mac, iOS and iPad apps outside of the ill-fated Vision Pro.

That's too little to late for me, but I think many will appreciate the benefits.

I've been trying to brainstorm a helpful use case this would bring but I can't think of anything.

I mean just imagine how jarring it is to go from touching the macbook screen to mess with your app to needing to input text. Whether you use the macbook keyboard, or the on screen keyboard, it's just kinda rough.