Yes, some shops are, and I lost count of the times when me, carrying a basket with a few items, was behind several other shoppers with huge trollies full to the brim. Pick a busy time and all the lanes are held up like this. Now we have self-checkouts for baskets only, and life works much better.

They still to have someone around, though, to satisfy the machine when it thinks that my newspaper is 25g too light, or I'm not old enough to buy alcohol-free beer (still haven't worked out the rationale for that one)