I have only been a (film) photographer for a short time, but I have thought a lot about this very subject. Personally, I feel there is one main dynamic at work which make B&W a much more powerful medium in which to work.
Since I see in color, color becomes mundane. Certainly, there are color scenes which are truly breathtaking and those that are deserve to be rendered in as vivid a color as possible. However, most of what (who) I see and photograph, I have seen many times in color and do not really SEE it (them) until I compose a shot in B&W. Only then can I really appreciate the shapes, tones, textures and relationships which are mostly obscured by the presence of color in my world.
Black and White gives me a whole new appreciation for vision and helps me really look at the world in which I am always immersed.