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). They could extend this by fitting onboard generators powered by (say) internal combustion engines, but this would not only be noisy - I think the public acceptability of petrol-containing drones flying around would be even less likely than for the electric flavour.
I also struggle with the implied assumption that delivery drones would be exempt from the vessel-vehicle-structure-person separation rules which currently even apply to a 1 kilo radio-controlled model aeroplane.
PDR
PS - High Colin [it's Pete R]