At least in Finland, self-checkout works pretty well. Stores of all sizes basically have them, at least in Helsinki. If there's over four machines, there's almost always a person standing by just to help the customers with any issues. In the larger stores, I've often seen two people dedicated to that. If there's just two machines, it's always right next to a traditional checkout with a cashier.

Cashiers have never been the ones tasked with bagging our groceries over here, so I guess it's not that big of a step to just scan and throw it in the bag after that.