In the case of Walmart their machines aren't set up well for large orders, you basically need to get a second carriage, if you try to stack up the full bags, you're guaranteed to get the dreaded...
Unexpected item in bagging area message, you could pile them on the filthy floor, but I'd always get the customer a second carriage.
A large order is likely to contain an age restricted item requiring my approval, then you get stuff that just won't scan, or an idiot trying to pay with a check. I have to fix all that stuff taking me away from watching the screen and trying to make sure stuff scans when people throw it in their bag.
Stores lose a lot of money with these imperfect machines, and that's in a fairly wealthy area....Old Saybrook, CT.
There's no real way to tell how much of lost inventory is from say employee theft, self-check, vendors ripping off receiving, and so on
WM will surely continue with the machines. You have to know what to expect when you walk in the door, minimal sales floor asses and cashiers, don't go there to get a key made or custom paint mixed, there might only be one guy on duty that can do it, likely the same guy, he could be on lunch, most asst managers don't know how to mix paint, they might cut a key, which may not work, that's why God founded Ace Hardware