Having the note text in the URL can be good in some cases. Storing the note as a bookmark becomes possible, as does storing a note in a URL shortening service. Opening a fork of a note from a different device also becomes possible this way. (eg. on Chrome, using "Send to Your Devices")

Localstorage (as far as I know) isn't easy to move across devices or share, and notes being a bit ephemeral is part of the idea of this. I think anyone who wants to save notes indefinitely is probably better off with one of the cloud-based note-taking apps.

One idea is that the url makes it immediately shareable. You can send your note to your phone in a text message without any uploads due to it being encoded in the url.