- Falible humans are “in the loop.” Human limitations and variability; human consequences. There’s a reason that CNC machine tools aren’t equipped with hand-cranks.
- Humans require anthropomorphisized flight information; visulization. One consequence is excess software and hardware overhead.
- Latency. Ask military drone pilots about this.
- Accuracy (presuming that the payloads are something other than explosives).
The military gets close (albeit often at high altitudes) and then uses a purposefully expendable vehicle to blow up things, using high explosives. Conceptually quite different from delivering chicken nuggets to someone’s driveway.