A full hack of every part of the service is not the only way a user's password could get known to an attacker. Could be MiTM, could be typo-squatted, etc
If a site is that compromised no measure of auth is gonna help, so little use worrying about it.
To be fair basically all services allow resetting passwords via email so even without the magic email link they'd be fucked anyways if their email got hacked.