Welcome to the world of holywood. Were the scotts defeated the engrish with nothing more then 2 handed cleavemores, wearing nothing under their kilts and screams of "FRREEEEEEEEEEEEDDOOOOOOOMMMMMMMM!!".

They may not be seen by the enemy but the archers firing them can't also. Suffering an accuracy penalty during night battles is a solid way to show the problem. It also gives a good bonus for non archer laden armies to have a decent shot at them if they have a solid general.