The rule of not flying over the crowds is important for avoiding any mishap just in case the drone goes out of control. The rule of not flying the drone over other people’s property is mainly related to protecting the privacy of the people.
This ban has forced Amazon to shift the research and development of Amazon Prime Air to the UK where it has been welcomed with open arms. This has, however, forced the new congress in the US to formulate regulations that must prevent this newest technology from drifting to other countries.