Dodgeing the Camera?

Why in the world would someone that was working as an extra be dodging a camera? I couldn't understand that when it was told to me, I thought the primary goal was to be seen? Isn't that right? Well it came to my attention that some actors when they are cast as extras unusually will find a way to dodge the camera. The reason why they do this is to get more days on the set. Ok, I can understand that to a point that you want more work, BUT! the more you dodge the less we others work, if that makes any sense. So please stop dodging and be seen :)