Besides, you can revoke permissions in your signing device, you can use multiple keys (I have 8 npubs), but you only have to add them to your key keeper once, same way we all keep our passwords in an encrypted PW app.
Discussion
By "one login", I don't mean "one key". I mean, literally, the workflow for logging in.
This is something that keeps people from using new software. As soon as they have to figure out how to login, they're like nah.
Nostr means you only need to learn this once and it isn't something propietary.
The workflow, sure, assuming all your devices support signing in with a key the same way (they don’t) but having to use multiple keys negates the convenience. At that point it just becomes a longer password.
I use Alby extension on desktop, Nostore on iOS, and several other apps just accept a nsec. A simple unified signin system may be the goal, but we’re miles from there imo.