I observe the click-click-clickers too and believe they are monumental idiots that not only endanger themselves, but other passengers as well. And all this for no good reason at all.

Watch the video, taken by an amateur in JFK, of an AirFrance A380 touching a smaller plane and spinning it around and imagine you where sitting in the small plane not buckled up:

http://www.bbc.co.uk/news/world-us-canada-13054205

The reason why this behavior mystifies me so much is that by jumping out of your seat prematurely you will be leaving the plane exactly 0 seconds earlier as when you remain buckled up until the plane is safely parked at the gate.