In the holiday season, the local Costco stores have people with a hand scanner standing in the checkout lines before the register. They scan every thing in the cart, scan your membership card, and all you have to do at the register is pay. Things go much quicker when the cart does not have be unloaded and reloaded.
Huh. I've never seen that here. Though I've noticed this year that, holidays aside, the second person at the checkout will stop me from putting as much stuff on the conveyor. It used to be just heavy stuff, but now it seems to be most stuff. Which ties into the "faster without loading and unloading" hypothesis.
I also never take boxes from them anymore. I bought one of those fold up "milk crates" they sell there and keep that in my 4Runner. Then I just load that up with the smaller stuff and it's way easier to carry than a random cardboard box. Plus then they don't have to pack stuff for me and the line goes that much quicker.