Couldn't they just use weather proof packaging instead?
But one of the bad side effects of "free" delivery is a race to the bottom in quality. My neighborhood UPS guy is awesome -- he rings the doorbell, if it's raining he puts a bag around each box, if a box is heavy he'll bring it inside for my wife. The local Lasership folks (different ones every time) are far less awesome -- they just drop the box on the porch, not bothering to ring the doorbell, not bothering with weatherproofing. So we've had a couple of boxes soaked, even when my wife was home, because she didn't hear the delivery.
I'd pay a couple bucks more to get UPS over Lasership, but it's not easy for me to select that option with most web merchants.
Heck, sometimes when import duties had to be paid upon delivery, they would stay upwards of 20+ minutes while I went to a nearby ATM. In those cases, they could just as easily have taken the package to the local post-office for collection.
Amazon re-ships via UPS/other and it arrives acceptably. The worst UPS has done is not knock/ring and that's rare.
90%+ of my packages via Ontrac had forged signatures, misreported delivery statuses, not actually arriving, [...]
Anyway the drop box idea is a way of securing the package vs just leaving it in the parking lot or whatever. A drone sure can't knock on the door and hand it over.