Grocery bagging specifically is an interesting point culturally. Bagging helpers do exist in the UK, but 99% of the time you will bag your own groceries as the cashier scans them. It gives you something to do while waiting, and enables you to pre-organise the bags any way you like.

There is something of a time loss if you can't keep up with the cashier, but that's not often much of a problem. The few times I or my husband have started bagging stuff in grocery stores here in California, though, we've gotten strange looks - and often, at Trader Joe's, where the cashier often bags after scanning everything - words of thanks.