It's irresponsible to forget to scan items as a  cashier.
Stan works as a cashier when someone comes with three carts full of groceries, just before his break.
Stan wants to go on break quickly.
Stan calls someone over for help, so they can get through the carts quickly and accurately.
Stan scans the items as fast as humanly possible, missing a few here and there.
Stan's draw balances out at the end of the day.
Stan's drawer is short $15 at the end of the day, and he gets in trouble.