content: Beacuse its inefficient. The control aspect is easy. The each drone use accelerometers to know which motor should be spun faster. If you take one of the drones and hold it flat, all 4 motors will spin; if you tilt it only the motors on the lower side will turn. Meaning each done only controls its 4 motors. Thats about as much time as I am willing to spend on this but here is a video to help ya. https://www.youtube.com/watch?v=KZVgKu6v808