Earlier quoted context omitted.
The thing that makes rural areas inefficient for trucks (distance between customers) is far worse for drones. Drones have to be based out of somewhere close to the customer due to their short battery life, which means you have to have a lot of bases, each of which only serves a handful of customers. A truck will burn a lot of fuel per customer, but a single one can still serve a large area on one tank and can be base…
A truck will burn a lot less fuel per kg of cargo. That's because it is carrying many packages at once and fuel consumption is split across all packages. A drone only carries one package. So in reality a truck is a way more efficient way of delivering good.
A truck gets that for free via tyres and tarmac.
Air travel makes sense for high-value and time-sensitive payloads, most especially passengers, but also communications (airmail delivery was, and remains, a significant revenue source for airlines).
Fixed-wing drones (as Zipline uses in Rwanda) are more efficient than rotary craft, as forward velocity generates lift, though at a cost of being unable to hover, which makes point delivery to locations lacking a landing strip (or other capture device) more challenging. Zipine utilises parachutes (and lightweight cargo) for its deliveries. Pivot-rotor craft (which Zipline seems to be experimenting with for urban deliveries) make hovering more viable whilst preserving the efficiency of fixed-wing flight.
I still see this as an option with very limited applicability.