Ask HN: Auth by Phone Instead of Email?

Seems like for simplicity, using a cell phone instead of email account registration and login is the way to go. Email seems so outmoded in the world of mobile communications. I think using a mobile number with some form of Authenticator for important stuff is reasonable. This would bypass all the Social logins, email deliverability and help create uniqueness as well as remove passwords.

How far off am I in thinking this is an ok thing to do?