When working in a distribution warehouse the only thing that matters is how many packages you can get out the door. On a packing line everything is done as efficiently as possible and this also means using the same sized box. They'll use bigger boxes because that'll increase the amount of orders that will fit into one. A one size fits all if you will. It saves time if you're sending out thousands of packages everyday. Someone doesn't look at your £1 USB cable and think 'Hmm, what box would be best for this?'. It gets thrown in a box, stuffed with padding and sent through the sealing machine without a second thought.