I think that Bungie needs to use low sensitivity in order to run the game smoothly. Its hard to describe, but Destiny is using really complex game engine. Where ever you look at (FOV) the game will load and display the information in front of you. All the information like obstacles, enemies and so on in the backround will be "deleted". This means that all the power from the console can be focused to only what you are seing. Now, imagine a fast sensitivity. Consoles could not keep up with the information when you spin around or something. This would basicly means that you will see heavy frame drops, and Bungie wants to give us smooth gameplay experience. Sure i might not be right about this, but thats my theory. There is a good reason why the sensitivity is so low.