The problem is that customers don't remember basically anything. I don't know my telephone banking password for any bank. When I call, I get asked to tell them what my last transaction was, or my mother's maiden name and DOB (public info), or what town I last used my card. I've been wrong about the recent usage questions more often than I've been right, and they say "close enough".

The technological measures have to account for human behaviour. Otherwise you just end up with almost everyone not being able to access almost everything almost all of the time. People are forgetful, irrational, stubborn and stupid. So are institutions. Put them together and you have a social engineering dream world (literally our current world).