It does happen, though. On occasion, I'll happen to have my camera with me and see something that makes me want to capture it. This is a good example (although, I didn't actually get the picture I wanted; I was too slow taking the picture):
One of the things I really like about my camera is the ability to perform some basic post-processing effects in-camera, such as the "grainy black & white" this picture uses. In case you wonder, I use a Canon Rebel T3i - it's quite a nice piece of equipment.