Walmart has a revolving bag dispenser/holder that holds bags open while the checkout person loads the items directly into them from the conveyor thingie, and holds the bags until the customer takes them off and puts them into their cart.
Walmart has started selling the re-usable bags, though. It will be interesting to see how the checkout people deal with the re-usable bags. So far, I haven't seen anyone use them. I don't, myself, because I use plastic grocery bags as trash can liners. That seems to make a lot more sense and to be a lot less wasteful than buying trash can liners just so I can throw them out.