Yebbut...some customers don't help themselves. Like the customers who write their PIN on the back of the debit card because they can't remember it, or those who say 'well...he was a lovely man from Nigeria who said he would pay me back 1.5 times what I lent him'.
My mother keeps her PIN written on a piece of paper in her purse with her card. When she had her purse stolen by distraction thieves in town, they went straight round to bank and emptied her account. As far as I know she still does, there's no incentive to change when the bank just gave her all her money back.
When "that nice man from the Halifax" rang up and told her he'd got a tax rebate for her, she gave him all her account details too.
"But how did he know I had an account at the Halifax?"
"Because you gave him your account number mum"
She's on every sucker list in the world now, but she won't change her phone number.
The only example of bank fraud I have personally is when I lost about £800 because I was lied to by a building society. Actually, that's
would have lost, because I got it all back when I complained.