Not to mention the last-foot problem of placing the package somewhere safe for the recipient. How would these drones put a package in a locked vestibule or even my covered porch?

Drones from the truck to the door would work, however. I could see the elimination of the driver walking the package to more of a drone operator to dump the package on the doorstep. Automation could queue it up so they could just put it in park and fly it... or even have remote operators picking up the package from a truck to the doorstep.

Even if that was technically possible, it sounds like just putting these last few meters into the hands of the driver who's in the car anyway (yeah, I know, level 5 self-driving tech will solve that problem in 2020 as well - another one of those dream castles in the sky...) would be waaay cheaper.

And more flexible: not everyone lives in a standard American suburb home with a garden, a veranda and doorsteps in front of it. Lots of people live in multi-tenant houses without gardens, even without doorsteps - or if there are doorsteps, they end directly on the street, so anything left there is stolen within minutes. Hypothetical drones would have to ring the bell, fly through the staircase (without chopping off anyone's head in the process), find the right flat, maybe ring again, leave the package and find back to the car.

This task gets fully automated as soon as someone is able to produce an affordable and reliable human-like robot (in terms of extremities) and outfits it with an actually working AGI. Before that happens, it's cheap labor exploitation galore, and if the government should intervene in that reckless exploitation, maybe coupled with people shifting some of their deliveries away from their doorsteps and to delivery to pick-up stations (because of incentives like that being the only free delivery option, or being the fastest one).