Not only is it rude, but at least here in Oregon it is also illegal.
One method that I frequently do not follow is the "dont sheet pkgs in the car" rule. The methods say to load the pkgs onto a carry aid, take them inside, line 'em up and scan them. I have bulk stops where there is no room to do this. Intead I scan the packages as I put them on the handcart, slide the cart down the back bumper, wheel it in, and slide the cart out from under the stack of packages. This saves room and minimizes package handling.