This whole drone delivery thing is a publicity stunt.
First off it takes a skilled operator to fly a drone. A friend of mine has learned to fly a 1/20th scale helicopter. He does it well. But he has spent a lot of time learning and he still has mishaps. With drones your delivery driver has to be a reasonably competent pilot. And don't tell me "computer control". It will be a long time before we see self flying drones.
Second, as pointed out, a drone out of control can kill. With a truck out of control you slam on the brakes and it generally stops. With a drone out of control if you slam on the breaks, i.e. turn it off, it falls from the sky. To do anything safe with a drone you have to regain control to land it safely.
Just imagine if in your car or truck when you started to loose control you could not just slam on the breaks but had to regain control before you could stop safely.
Third, legal liability. When the drone falls from the sky or crashes into something, who is going pay for damages? If it kills someone who will pay for the law suite?
And the last thing is power. If the drones are battery powered how far will the get on a charge. My guess is that it would be measured in 10ths of miles not 10s of miles. My friend who flies helicopters gets 10 to 15 minutes on a charge with no payload. Drones that can fly farther are gas powered and are really small airplanes which need runways to land and take off.
I love to read about drones and drones delivering packages. They are great. But I also love to read about stunners and phasers, transporters and faster then light interstellar travel. But I read about them in science fiction not in business plans.
Drone delivery in the foreseeable future is just a publicity stunt, AFAIAC.