One graphic technique for high definition colour works like this: You take a very high resolution black and white (grey-scale) image, and overlay a low resolution image that contains colours. The result looks like a very high resolution colour image but in digital form, it requires a lot less storage space than an equivalent high-resolution colour image. Now, the reason for this is because most of a picture's information is conveyed by value. In art, we deem 'value' to be the amount of light that an area reflects. Our eyes and brain are set up to interpret value very well. A low resolution swash of translucent colour over this adds hue without affecting the relative values too mush. Your impression of sharpness is not affected significantly. This means that our native appreciation of an image is highly dependent on value, not hue. This is why black and white photos can look very nice.
Sometimes, depending on the subject, mood, balance, weight and composition, a good black and white image can wash away value-distraction imposed by hue and deliver an impressive image that somehow out-shines its colour equivalent.
Additionally, there is a nostalgic theme to black and white photography because of the history of photographic tools and techniques.