I'm using the same technique but at the checkout. Once my reusable bags fill up, I leave the rest. Also this technique helps in letting go of that packaged/junk food at the checkout.
So instead of just not grabbing junk food, you leave it to make more work for the store employees? Unless you restock the shelves yourself, that is incredibly inconsiderate. Also, if an item is frozen, refridgerated, or fresh produce it likely ends up in the trash as spoilage, since a busy cashier won't have time to restock abandoned items.
Also, aren't items already scanned before they enter the bag? I don't understand how leaving the rest could actually play out unless the cashier had to then void each one.