There are other more practical obstacles. Current battery technology would limit drone delivery devices to rather short ranges (perhaps 3-5 miles) with any significant payload (much more than a couple of kilos).
Amazon's latest prototype drone can already fly 15 miles with a target payload of ~ 5 lbs (2.26 kg). Currently, more than 80% of Amazon orders are under 5 lbs.
The drone is a hybrid design -- it is an octocopter with vertical takeoff / landing, but also has wings and a pusher prop to fly like a conventional rc aircraft to/from the destination.
https://www.washingtonpost.com/news/...-worth-noting/