Common in my opinion for small items to be placed in ridiculously large packages .
"Never ascribe to malice what can be explained by stupidity."
I'd say lack of care rather than stupidity, but more likely just different priorities.
(Longer than expected rant about shipping methods below ... TLDR boxes and shipping cheap, employees expensive)
Having worked in a warehouse packing orders years ago, number 1 priority was get the stuff shipped. Didn't matter if we had 3 orders or 30 orders. Everything had to be packed and ready by 2pm when our AusPost truck would show up for pickup. The perfect box doesn't exist, so you make do. Always bigger, because smaller just doesn't work (duh). Trying to pick and pack into the box as you go is often fastest, because otherwise you're double or triple handling things. So you grab whatever box you have that you 'know' will fit everything, and you get the order out the door. If you have to unpack and repack because you picked a bad box you're wasting time. If you hunt around for 10 minutes to find a different box you're wasting time.
I'll bet they measure employee performance on boxes packed, not box efficiency. Employee time may be more costly than the additional shipping costs or larger boxes.