Comment by pmontra

I can share links to myself with a messenger but it's much faster to share them to a given device and see its browser open a tab to that link. It works inside apps too: I can share a video from phone to tablet (NewPipe, probably YouTube too, it's the Android builtin sharing system.)

I can also stop, resume, control volume of media playing on another device.

I can share the clipboard, send files, use a remote keyboard (I think I disabled it) and ping a device.

It can do a lot more but I'm not using much else, I think.