Urban areas are already pretty well optimized by the traditional system. Urban population density makes good use of a delivery van's cargo capacity. Drone deliveries would make more sense in suburban or rural situations, where a drone can be more efficient than a whole delivery van traveling somewhere to deliver a single package.

If drone delivery doesn't work in a metro the size of Los Angeles or Cincinnati, then it doesn't work anywhere.

Self driving cars are a much more difficult proposition and we can already do that pretty well. Flying where there is significantly less traffic and less obstacles and a third dimension to use? That makes things very easy.

Piloting the drones isn't the problem- the problem is logistics, noise, regulation, costs, etc.

Why do they have to use it in urban environments? Huge numbers of people in the USA live in a suburb.

This is a pedantic argument.

It can take the Telsa approach and record millions of hours of manual "highway in the sky" trips. Then compile and go from there.