How do you solve the problem of needing to pass an email address via phone? Happened to me dozens of times over the last year. Also, how do you solve the problem of shared inboxes where employees need to access emails and they may get replaced over time? How do you solve the problem of people just straight up losing or breaking their keys/laptops/phones? I knew people who had a new phone every few months because something happened to it.

The average user is very, very far away from being able to use a nearly irreplacible item for communication. And yes, it's irreplacible since there is no rollover mechanism in just publishing the public key.