Because there will always be people like my mom who can't remember their account PIN but get super pissed when on the phone, ask to speak to a manager, etc...

Because there will always be people like my mom who can't remember their account PIN but get super pissed when on the phone, ask to speak to a manager, etc... Defending against social engineering attacks is HARD, because the only real mitigations against them could also result in locking out the real owner of the account.