It doesn’t help that many times a customer will bring a shopping cart with a gazillion items in it to the self checkout lane then spend nearly 30 minutes scanning it all. Those scan and go machines were installed so folks with just a few items could scan and go in just a few moments. Instead you have to wait because people misuse them, and they don’t care how they are inconveniencing other shoppers.
I prefer self checkout because the staff who do the checkout tend to be very sloppy in packing.
One case I remember is where the checker put a lot of cold items into one bag, and when it became full, put the small ice cream into the next bag with nothing cold near it — on a hot day.
Another time, I explained to the checker how I wanted things packed, and she did it that way — until the kid came over and took over the packing — doing it randomly, of course.