Well not only all of that, but it makes it much easier to know whether or not the device is actually on or off. I realize this is the iLiad forum, and there may be some indicator of its power state, but on the Sony Reader, if my screen always kept the last page viewed on its display, I would be changing pages back and forth one time just to make sure it was on or off (to avoid accidental page changes while not in use, etc.).
edit for addendum:
Actually, I guess I would just hit the joystick instead of actually changing pages back and forth, but you get my meaning.