Michael B Sullivansees the implementation of Amazon PrimeAir much the way I do, as the last part of integrated logistics:
Taking as the basis for conversation a world in which both drones and driverless vehicles are technically possible and easy-to-use (I don’t think either are right around the corner), then I think you use both for your delivery.
Forget last-mile delivery, this is more about “last 15ish miles” and “last quarter mile.” You send your driverless big old truck out with hundreds of packages. It has with it a small fleet (maybe 5-10) of drones that handle the last quarter mile of the delivery. Your truck trundles along on big streets that can accommodate it; the drones blitz out with packages and back over short distances, charging up from the big batteries of the truck on a rotation. This allows you to deliver far heavier packages (the drones don’t need a battery capable of delivering X kg over 15km, they need a battery capable of delivering X kg over 0.5km), at overall lower cost (the majority of your trip is via low-energy rolling along roads, not high-energy helicoptering), but with the same convenience of the actual delivery (no giant truck moving along narrow residential streets, no need for some kind of klutzy mechanical linkage between a robotic vehicle and your drop-box at your house). It’s probably less legitimately awful in terms of aviation control, too.