Any one with even a small bit of experience piloting a drone knows that there are a 1,000 things that can go wrong when drones get in the air.
Videos (like this UPS video) are like videos promoting driver-less cars or 100% safe space flight or a 100% safe anything for that matter.
When lawyers get involved with the first serious accident involving a remotely delivered package, the idea of future such deliveries will come to a screeching halt.