I absolutely agree that images benefit from black and white tones. I believe images benefit from having a black point, three-quartertones, midtones, quartertones, highlights and a white point. The inquiry is to what extent midtones may be of greater perceptual significance. A photograph could be taken having just three-quartertones and highlights and be simply breathtaking but that is beside the point. Most photographs published in magazines and newspapers are not that esoteric. In fact, perceptually, there exists an ideal (albeit not a magic ideal) formula of tonal distribution that results in a more captivating and more visually communicative photograph. This simply must be true weather there has been research in the area or not. Given a survey, with a statistically significant population, a normal distribution of responses would demonstrate a human preference for particular combination of the above tones. Stretch those neurons. I haven't seen that happen yet.