Why aren't we using drone blimp/hybird airship for delivery?
There are many reasons why that will probably not happen.
Number 1: As of right now drones/blimps are very big for 1 package. It is much more efficient to use a car that can take in hundreds of packages.
Number 2: There are may types of drones/blimps that can be flammable exposed to certain chemicals. Also...where is the drone gong to fly? In airspace where planes are? Where is it gong to land? What about apartment buildings?
Thats why this is not plausible. Maybe one day it will.