Funny how people buy a single small item have it shipped to them then have the gall to complain about shipping waste.
Contrast with you personally making a detour in your car to a physical store to buy a single small item -- that actually DOES have a fuel cost.
Unless your purchases are always along a route your travel anyways (like your commute), delivery is vastly more fuel-efficient as a general rule.
Amazon does this a lot, no matter what your order looks like. The most pathological I've ever seen was at an old workplace, they shipped 20 boxes of pens (12 packs or whatever size of disposable pens) each in a separate large box. The delivery person took several trips up the elevator to deliver them.
But, of course you have an answer to this problem, right?
Obviously, Prime also pushes people toward single-item orders, which helps justify this strategy, and also increases people's dependence on a service level that is hard for competitors to match who aren't at a scale where these kinds of approaches work out.
Kind of a fail that the system wouldn't flag a 20-parcel order as something that needed a human to ok it, but who knows, perhaps it was reviewed after the fact and something got tweaked.
In order to discover how much waste there is in ordering 1 thing one day and one the next you have to determine exactly how the route would have differed in each case. Given the delivery truck would probably still have been in your town anyway lets imagine for the sake of argument that it drives an additional half mile each way. If we try to imagine the net effect of lots of extra packages lets say all the extra packages in the truck caused a net of 100 miles of travel divided 100 ways. So lets imagine a net cost of 2 miles of travel. So the person probably wasted the equivalent of 1/5 of a gallon of gas.
More efficient delivery trucks which fedex and ups are rolling out will make a difference. This relies on a few parties that will directly benefit from doing so. Totally going to happen.
Less packaging by actually putting more than one thing in the same exterior packing would make a difference. This relies on a few parties who would benefit slightly. This might in theory happen.
Batching orders instead of ordering item A when you actually need it and item B when you need it doesn't matter much and would be difficult to do. It requires millions of people to think ahead and always order things before they need them. This will NEVER happen.
The people complaining about shipping waste are addressing a legitimate problem that actually could be solved. Your statement is akin to the people that say why do we need to work on problem foo while their are still children starving in Africa. It's true their are and we ought to do something but in the meanwhile we can still do other things to.
There was multiple items amazon decided not to bundle.