The reason why you don't see any commercial drones, despite of their desperate need by companies like Amazon, is simple- it is illegal. The Federal Aviation Administration of USA, and other similar organizations in most of the countries don't permit the commercial use of such drones.
The reason why these organizations don't allow companies to use such commercial drones, despite the fact that it would greatly reduce delivery times, is because these companies could misuse this facility. For instance- they could easily spy on you. Also, they pose a threat to airlines, and the aviation authority wants to keep the sky as clear as possible.
Looking at the flipside, drones could be used for many good reasons too. For instance- drones can readily assist the police and the army in search and rescue missions, since they can reach some of the roughest places, which are risky for a human life. Movie makers have also used camera equipped drones for breath-taking videos to be used in their products.
Comparing the both sides of the drones 'usage, it is hard to tell what their future looks like. However, for now it seems very unlikely that the drones will see their commercial usage. Many companies are using them in lingo, and are well aware of the fact that they could be shut down any day. One such operator was recently fined $10,000 by the FAA.