It's not like it actually helps, it's like playing with the blind skull on, you still fire from the same place every time it's just a matter of if you're used to it or not, putting something on your screen doesn't change that. Hell, in a lot of games it would actually hurt, take battlefield, the laser sight points towards where the gun is actually pointing, and moves around, same with iron sights etc., if you tried to use a static dot where it would be when you are standing still it would not be where you should actually be aiming unless you were standing perfectly still.