- So that users could access their account from multiple devices at home / work, desktop / mobile etc.
- The Site/app developer had some way to reach the user for various reasons. They needed not just an identity but also a communication channel.
But today's browsers already support syncing across multiple devices AND push notifications.
Combining both of these, we can do away with signup and login forms - simplifying the UX a lot AND avoiding privacy dangers that come with server-side registration using email address / phone etc.
We may need to provide the users more control on filtering, searching, and archiving browser push notifications, but this would be a one-time effort per browser and would actually be much more empowering. We could even support multiple accounts using containers in browsers.
Has this been attempted? As a user, will you prefer this?