It seems like a pretty easy fix would be WYSIWYG and you can only hit what you can see. Only those that can see a target can shoot at so the reciprocal would make sense and doesn’t add any complexity to the game that I can see.
To repeat what was said earlier, the answer is simple – game balance (it stops you poking one guy out with say a rifle to put a pin on a unit while keeping the rest untouchable.) and to help (as the rulebook says it the same paragraph) give the impression that everything /model is fluid and in motion…
