Grocery stores used to have you bring in a list of what you needed and the grocer picked it all out for you from behind the counter and packed it up. If you walk through a store and put your own groceries in a cart, you're already doing free work for the owner of the store.

I wouldn't change that, and I wouldn't change self checkout. I prefer both. It's not work if I'd rather do it.

(The first paragraph is a true story, but also a joke. Doing "work" is all relative.)