Back to the story of the boy chucking beached starfish back into the water, without the man, it's just a kid throwing sea creatures. In order for the story to make sense, the man has to be there questioning the boy on what he's doing. There are a million times in everything we do that someone comes along and asks that very question: Why are you doing that?
These questioners come in varying stages of curiosity to aggressive, but there is almost always a questioner around to ask why you're doing something. Just as there is usually someone who doesn't understand how important what you're doing is. My theory is that these people come into our lives to help us clarify, even just to ourselves, why we're doing what we are doing. These questioners are a magnifying glass helping us focus and see from a new way the impact of our actions. That's a lens and a focus we never would've seen through were it not for the questioners in our lives.