My opinion on these features is that they are not very realistic and possibly overly complex. Commanders in real action can hardly determine precise lines of sight based on maps, perhaps somewhat better in modern situations, not to mention areas of sight. Such features induce micro-managing of positions of low level individual units. The complexity increases anxiety by adding extra aspects to the already intense planning and execution. I think they do not to be disabled, just the player do not need access to such precise information but just some more general one, though the system may still make calculations based on it. And the same applies to overlays except possibly for Movement. And simplifying some minutiae may help to bring more players and consequently funding.