I didn't see any packages dropped off right at the door, did you?

Or...better yet, there would be a self-driving truck/flat-bed which drives close to a certain city-center area, and has on its bed a mini-fleet of drones, these drones will lift-off from the truck instead of the fulfillment hub...these smaller drones would deliver it to the front door. Alternatively, the self-driving truck could have a cartoon-like robotic arm that extends to the customer's front door; ringing the doorbell automatically and dropping the package on the doormat. ;-)

Slingshot. :)