It's 100% that. One of the grocery stores near me has no weight checks or baggage area rules. I can easily bag my groceries into my backpack directly, at other stores my backpack is too heavy to be considered my bag and so if I want to do that the attendent has to override it so I never bother. Then since there's no weight check you never run into the "unexpected item in bagging area" or "please place item in bagging area" issues ever where the scale/item weight isn't acting as expected.