Our local Costco used to have a scanner gun at the self-checkout. I used to be a grocery cashier who prided himself on how quickly he could scan someone’s purchase. So I’d arrange my cart of stuff (for a household of six) in such a way that made scanning efficient. Then one day I get there and the scanner is gone. If I have to remove every single item from my cart I might as well use the conventional check-out because now self-checkout is far less efficient for me.