I used to be a cashier. When you're standing in one spot for 8 hours at a time it's impossible not to space out. I'd work on novel scenes in my head and just go on autopilot often. The dividers are nice since people stack things stupidly. Some people will have random gaps in their order since they can't unload as quickly as the belt. Though if you grab someone else's order they usually stop you after 1-2 items so it's no biggie. I only use self checkout now so I never have to worry about people.