This. I used to work in a supermarket. Courtesy clerks (baggers) and even cashiers could be given bizarre tasks during slowdowns, but the crowds would always pick up during their shifts and they'd need to be called back to their posts. Seemed like this was usually at the top and bottom of the hour and various rush points of the workday. If the overflow labor wasn't there, lines would back up into the aisles and customers wouldn't just complain, they'd go bonkers.