Couple of points, first of all the thing the browser can still remember is the auth token in a non-expiring cookie. As the majority of users will rarely if ever clear cookies or change browsers, this nullifies the password remembering feature.

Secondly, particularly on mobile, tapping through to email and hitting a link is probably faster and more convenient for most users than simply entering a password on the keyboard.

It's just a shame it's such a pain to write automated tests that go through the email login procedure compared to username/password ;-)