My SO works fast food. Corporate never allocates enough hours so they're perpetually understaffed, but the store manager has permission to call people in if needed. So there's a lot of "your scheduled 10-4, but at 3:30 I'm gonna ask if you'll stay to 6, or I'll call you 2 hours before your shift to see if you can come in early".
Its a lose lose, nobody gets the hours they want, manager can't retain workers, people hate being called in or asked to stay late, and the schedule is always shorthanded and mostly a suggestion. Of course nobody wants to work in that shitty mess of cost cutting and begging employees to pick up the slack that the MBAs at corporate have caused.