In a passive-matrix LCD we have horizontal and vertical conductors. The intersection points are pixels which are cells of liquid crystal molecules.
For drawing a frame, we provide the necessary voltages to specific conductors. But once we have provided the voltages and the picture has been drawn on the screen, why do we need to refresh?
As long as the voltage is on the picture is still there; it's not like a CRT where the emission from phosphorus atoms decays. If the reason is video or animation, then we are changing the frame buffer and then drawing the new frame buffer. But do we need to refresh the same frame buffer at some rate? If so, why?