You can see the reason for this if you move your eye slowly (by following a moving object)— say, place your cursor under a line of text and move it across the screen, following it with your eyes. If you do this right, you can notice motion blur in the surrounding text.
Now look back at where you started, a movement that takes tens of milliseconds. Imagine how much blur that creates— that image must be completely useless. You're doing yourself a favor to ignore it.
Edit: Since I mention it, I've wondered before if there'd be any value to training yourself to move your eyes smoothly without following an object. This test suggests probably not; the image just isn't good for anything unless it's correcting for a moving object.