This amazing concept of Amazon met with a failure due to the regulation by FAA, which prohibits the use of transport drones for commercial purposes, citing the safety and security issues. The concerns are mainly related to the safety of the people and their property over which these transport drones will be flying.
If they go out of control, they may cause life threatening accidents and do irreparable damage to properties. Although there is not much documented evidence to prove this, it is always important to put the safety of the citizens first.