I suppose in most cases, for most people, this would be a positive externality. You get free stuff. Amazon should just do a better job communicating this.
I've more than once got complete garbage through somebody getting hold of my shipping address (not credit card, just shipping address!) and exploiting Amazon using it.
I get 'free stuff' except it's absolute garbage. Somebody else gets to abuse Amazon reviews, hyping that stuff under my name for the purpose of jacking up its review scores. Once I looked and the thing was rated #1 in its category.
Don't assume you've figured out the true costs of externalities: anything that is clearly a broken system is also going to be harming people in its brokenness.
The only time that I got someone else's amazon package, likely due to a labelling or packing error, it was utterly useless to me, I mean like "book 4 of an anime series that I had never heard of, not in a language that I understand" level of junk-ness (to me).
It's typically not "free stuff" to the recipient, it's junk, a hassle, and in the way.
The "spam parcels" from review-brushing scams have negative externalities, yes; but, unlike regular spam, these spam parcels don't make up the majority (or even a non-negligible minority) of Amazon deliveries. So, on net, a random abandoned parcel pallet is going to have net-positive ROI to whoever claims it. Probably highly net-positive ROI.
(Compare: the liquidation stores that run entirely off of a business model of buying Amazon returns lots, tossing out the broken crap, and selling the rest. Those stores make a profit, and they're receiving pallets where half the stuff is unusuable. If they were receiving pallets where everything is new from the warehouse [valuable or not], they'd likely cry for joy.)
Remember, whoever gets this stuff doesn't have to personally have a use for it. They could just call up their local charitable thrift store to drive over and pick up the whole lot, if they wanted. But that's still net-positive ROI — they get a warm feeling of having donated a bunch of stuff; and the charitable thrift store gets a lot of free stock that they know how to resell, to turn into money for their charity; and a bunch of people who each wanted one particular thing, can now find it at that thrift store for much less than they would have paid for it on Amazon. It's exactly the same as if Amazon donated a bunch of random crap directly to the charitable thrift store, save for the necessity of making one phone call, and the possibility of the caller skimming whatever nice items they like off the top before they make that call.
All of these comments are from the perspective of a consumer rather than the perspective of the amazon employee (driver) who is likely poorly treated and paid. I doubt the driver is happy about their situation, is that positive?
Minimally paid, so again probably not happy. You think people in low wage delivery jobs are doing it because they love delivering things? No, they likely don't have many other options, if any at all
I get 'free stuff' except it's absolute garbage. Somebody else gets to abuse Amazon reviews, hyping that stuff under my name for the purpose of jacking up its review scores. Once I looked and the thing was rated #1 in its category.
Don't assume you've figured out the true costs of externalities: anything that is clearly a broken system is also going to be harming people in its brokenness.