1, air regulations
2, only carry light + small packages
3, probably more expensive anyway
4, battery life
5, weather
6, people hitting them out the sky
7, sheer amount needed (think about how much is in every van)
8, what if yer not in or how to sign for for legal
9, going to go into buildings and up stairs? lol
10, people stealing the goods and the drones themselves
11, people can easy hack military ones never mind these
12, how people feel about millions over head and what happens when they drop out sky and kill someone
13, loads more I'm sure cant think right now
Fact is some of that can be solved but its just simply not going to happen anytime soon.