I wonder if this endless line thing is something typical in the US. I've been to many European countries and other than before Christmas, you never feel like staying in line is something to even think of, because the longest you usually wait is maybe 5 minutes.
In Switzerland, now that in many shops you get to scan the cart yourself (after shopping or during it) there is just no congestion at all, even on a busy Saturday.
How is it in your countries?
It's off topic but I am annoyed that every device has to beep at me constantly
FWIW, in Basel (Switzerland) there are often large queues at the weekends/late evenings in the (only) two supermarkets which are open, despite self-checkouts. They are relatively small stores near the station, and serve very high demand driven by Switzerland's opening-time restrictions.
I've seen great strides in recent years to advance self checkout technology and its user flow. Walmart is my favorite example of this, my local one having almost half of the area devoted to self checkout. It seems to have been successful for them so far. I don't see anyone having a hard time operate them and perhaps more surprising, it's filled me with the idea that I can pop in and out of a big store on a busy day to just buy 1 item.
Why don't the customers scan the items themselves as they put them into their carts while at the shelves, rather than waiting until they get to the checkout? That's what we do where I live in the UK.
Wal-Mart has a nice cordoned-off maze to keep the line under control - a simple solution that works perfectly.