The reason is also that when the camera captures such an event an actual person gets to look at it and take the final decision, instead of just acting like a robot and dispatching the fine. They will use common sense to decide whether it was a punishable offense.

This is also the reason why it's never a good idea to flip off the camera. A court decided that looking at pictures of people showing the finger would have an emotional impact on the person analyzing them later so the fine in this case is much greater.