Automatic password changing would be a mess if you ever got locked out of your password manager, combined with the fact that if the protocol for password changing was to be breached, you'd be locked out of that account as well.
The protocol isn't any different than it is today you need to know the account and the current password, there isn't anything more to breach then today it's no different than any password change form.
If you get locked out of your password manager you are already fucked.
And in any case It doesn't prevent users from reseting a password manually directly on each site.
You can export passwords from your password manager to a text file on a thumb drive, and store that in a safe, secret place. It's not perfect but works OK if you don't change passwords often.
