Black characters are only the result of light reflecting off the screen, not light being emitted from the display. In a dark room you would have a high contrast ratio, because the whites would be at a high level of light, and the black would be very low, because there is no reflected light. Reflective light offers the same intensity whether it reflects off black or white. In the absence of reflection, you will have a high contrast ratio. Unfortunately, most people do not work in dark rooms.
Most people work in brightly light offices where there are high levels of reflected light.
This ambient light will decrease the contrast ratio of the display, so a high contrast coating will actually compensate for this washed out appearance. The high contrast coating restores the contrast ratio to a level that will increase reading speed and productivity. In a dark room, there is no reflected light, so the contrast ratio is high. Without a high contrast coating, you can see that the difference between the black character and the characters is not as great as it was in the dark room. You can see a high contrast coating compensates for the ambient light in your office and returns the contrast ratio to a level which will increase reading speed and productivity.