Adding my experience. I was a driver helper at one point too, and my driver would deliver all the commercial/business packages first, then park in an empty area

Adding my experience. I was a driver helper at one point too, and my driver would deliver all the commercial/business packages first, then park in an empty area (residential side street or parking lot) and we would handsort the remaining packages along his personally directed route. We'd unload each package one by one, the driver chucking them to me from inside the truck with the words "right" or "left" and I'd form two piles depending on the word, then I'd toss them back. First one pile, then the next. He had his route memorized and after reloading delivery was super efficient. It blew my mind that we wasted an hour or so every day just to optimize something that could be automatic via a machine or at least implemented by the loaders... Sad to see it still hasn't changed.