Delivery Drones Physically Impractical

This is why I'm anticipating a vehicle/drone delivery system hybrid. Essentially an Amazon van will drive around, and the drones will fly off from the moving vehicle to deliver packages. Meanwhile, the driver starts and stops the vehicle as is typical right now to deliver the heavier packages.

> At least not until electric motor efficiency and battery capacity technologies make significant leaps. Unfortunately, they have not made dramatic improvements over the past few decades.

Is it really so? Why we keep reading about steady significant progress over the same period in batteries and even motors?

This article is very superficial - it mentions watts instantaneously, but doesn't get into the fundamental problem of energy storage in watt-hours per kilogram.

The very best lithium ion batteries are somewhere around 250Wh/kg right now. Now compare that to the energy storage in diesel or gasoline...