I am from time to time, asked for my receipt at Wally World, and I don’t see a problem with it. I see it as a random attempt at controlling store loses.
You see, the person who just checked you out may be a friend or relative of yours and they did not charge you for some items that are in your bag.
And some less honest citizens than you may not put everything on the conveyor belt to be charged for. I’ve seen more than one person leave some items on the bottom rack and say “oh I forgot” if the checkout clerk catches it.