If you work in photographic situations where you know exactly what is going to happen and when then I'll forgive you if you leave your camera in its bag.
But who of us can guarantee that? If you like to walk around and take photographs of your surroundings, then the difference between having your camera out and fumbling for it in your bag...well it will most likely be the difference between getting the shot and not.
My two boys were playing on this unusually designed slide in a park called Moerenuma. It's a massive playground, with a giant water fountain which spurts water 25 metres into the air at its heart. The whole area was designed by the famous Japanese sculptor Isamu Nogouchi and is filled with weird and wonderful structures all designed to be played on.
Anyway I was just sitting around, watching my boys play on the slide when this guy rode right in front of me. I only just noticed him because I was actually looking at something in the opposite direction. So I quickly brought the camera up to my eye and got off one frame before he was out of view. He's not even pin sharp because I didn't have time to focus and the focus was already set on the slide in the background.
But how cool is it? A really funky slide, in front of which happens to ride an old Japanese guy on a chopper style, bright red bicycle with American flags all over it. It was just so bizarre that I was happy just to get this one shot, despite its obvious imperfections. Had I had the camera in the bag I never would have got the shot and I would have to have told you the story about the great shot that got away. Keep your camera out!