I’ve seen videos of a firm doing interesting stuff with bigger “mothership” drones that hover much higher and then lower a much smaller drone like thing on a cable to place the parcel on the ground. They can hit pretty precise targets and can maneuver around more obstacles than bigger drones can.

All that needs to happen is for the tech to advance to the point where it’s cheaper to do x% of their deliveries via automated drones than it would cost to have delivery drivers do it and they’ll start doing it. Saving millions(billions?) by say halving the number of human operated delivery trucks will make it a no brainer for them.