I'm sure there's a surprisingly high frequency of "acceptable" collisions if the bar is matching truck-inflicted property damage and injuries. Much like with replacing human drivers with computers, though, merely matching the cost and harms of the existing system is far from enough. Entrenched systems benefit from familiarity with the associated costs and risks, and from any structures built to mitigate them. New solutions have to be much better to gain acceptance.
Fortunately, automated systems can meet that higher threshold so long as we actually aim for it. If you aim for the lower "beats existing systems by some measures" bar then you make stupid decisions and tradeoffs like rushing to market or leaving out more capable sensors. We ought to try to make new technologies as good as possible. Sometimes the market will bet against that, but that's a tide that engineers should fight back against. Trucks kill too many people, and if drones kill half as many that's still unacceptable. We can do better.
> merely matching the cost and harms of the existing system is far from enough
The new system needs to be better but that doesn’t necessarily mean safer.
For delivery, that could mean cheaper and faster and more convenient.
Autonomous vehicles are a special case because those accidents tend to cause death and serious injury. As long as delivery drones can avoid killing multiple people per year, they are probably fine to compete on other metrics.
If Amazon handled it the right way, their drone smashing through your window could be a mere inconvenience.
In comparison to the way their delivery drivers drive down my sidewalk, I can see the drone being a safety win.