You can also collect booty from parked UPS and FedEx trucks.

In San Francisco, at least, the trucks' cargo areas are locked and reasonably well-secured when the vehicle is not attended, to reduce the opportunity for exactly this crime. I'm sure there are areas where sniping a few boxes from a truck as the driver is otherwise occupied is not so difficult, but that's not something one could expect to get away with repeatedly.

There's a reason the drone is made to land going directly down, vertically, once it reaches the destination.

If drones do get shot down, I'm sure Amazon will eventually deploy escort drones that sense where the shots come from. lol...