Hmmm, I don't have a solution but if it was common for elderly people to have no passcode then they'd be a huge target for stealing them and emptying their bank accounts.
My Grandma's solution to this problem is to not bring her phone with her when going to public places, and that's probably the right call if you can swing it.
Which bank allows you to empty someone's bank account if you find yourself with an unlocked device in your hand?? If was a criminal I'd be waiting outside their branch and snatching people's phones out of their hands right there, so I'm pretty confident that's not a real scenario.
Still, blame the bank, this is an issue they should have fixed even before smartphones became popular.