They might have the ability to do so. The motivation? Well let me put it this way: I tried Amazon’s grocery delivery service, and stopped using it because everything—everything—kept arriving in its own individual bag regardless of whether it made any sense, so it was just a bunch of bags I had to carry upstairs. That bags also had no handles.
So they were optimizing for something, but it definitely wasn’t packaging efficiency.
Or the alternative that I occasionally encounter with non-grocery items - giant heavy item and small delicate item placed together in same box that is far too large for the both of them. A token piece of packing paper or lone plastic bladder tossed in, free to move about. The entire contents bouncing around.
Another amusing one was when they packed a somewhat delicate pantry food item in a paper envelope. It arrived thoroughly crushed, exactly as one would expect.
Optimizing for dollar cost. Human time costs more than the extra packaging.
Results would doubtless be different if they were optimizing for minimal environmental impact or produced waste.