Why do cashiers scan the products twice if they already scanned it once?

I’m going to a store that most of us know, the one where you got to be the cashier yourself. <br><br>I’m able to fit the items in my backpack and I’m ofc not scanning them when I’m putting them in the bag. When there’s an employee behind me, they will scan the items I’m putting in the bag again and put the “stolen” items in their shopping cart. <br><br>It seems a bit pointless if they need to give the items back to the stock afterwards. Anyone know why they do this?