Like many laws, it's not really supposed to act as a deterrent, it's just an easier way to administer the law. If you find someone flying a drone dangerously,

Like many laws, it's not really supposed to act as a deterrent, it's just an easier way to administer the law. If you find someone flying a drone dangerously, at the moment it's hard to know where to draw the line at what is legal, which then makes it difficult to prosecute someone who's flying drones recklessly (such as flying over airports). If you have drone registration, then in the same scenario you can either take away their license (an action which doesn't require proof beyond reasonable doubt) or if they aren't licensed, you have a very easy law to prosecute against (flying without a license).