You can do a lot more with the ability to display using the whole field of vision. That's just a fact. If you can also use better control systems (gestures, etc) and interact with a visual environment those are also big benefits. You're right that the glasses form factor can't get near that right now, but we know that headsets can (like the Quest).

I am also of the opinion that Apple really messed up the watch ecosystem by locking it down so much. They prevented us from fully utilizing web browsing, text messaging, wouldn't allow spotify streaming for years, etc, not because of the watch being incapable, but because they wanted to maintain their walled garden and didn't trust watch owners to be able to type on a watch. If they allowed these things the watch would have been much more successful.