Here in Toronto, we have both. In fact, one location of a grocery chain might allow you to tag and weigh your own items, whereas another location of the same grocery chain might require an attendant (usually right next to the automated machines) to verify it.

I've seen one location go from requiring an assistant to allowing full self-serve.

Not sure about the U.S. but I have the impression that there must be places which are similar in the U.S.