You know where he is versus you don't know where he is. If he's jimmying open a sliding glass door, he'll just maneuver himself between the wall and the flashlight. If he has a gun and willing to go the distance with it, you'd rather know where he is then not knowing.
So, this is a guy, still outside your house, who sees you with a gun, and rather than take off and try the next house, is going to try to have a shootout? Seriously?