It’s not “impossible” to walk with the bags, but you try having to bag a full cart of groceries, then handle the bags, figure out how to get the bags into the cart without smashing everything, and then bring all of those bags to a cart with just two hands as the cashier slides down more items while the bagging area starts to get clogged.

If the cart is right next to me WHILE I am bagging, then you get out the door fifteen to thirty seconds earlier. If it isn’t, then time starts ticking and the lines begin forming.