I did see an article fairly recently in which retail stores that replaced human cashiers with automated checkout lines found that human customers needed a significant amount of help using the terminals, so that the companies couldn't reduce staff as much as expected. The automated checkout lines were also not significantly faster, on average, than human-staffed checkout lines.

And customers were getting very frustrated over it.

This doesn't even count the claims about massive increases in theft.

(My personal thing has always been that if I'm going to do work myself that you otherwise would have paid someone else to do, you need to split the savings with me. Well, that and you need to pay for employee retraining.)