[Chimaera182]

I was going to say something similar, but Chanak pretty well nailed it on the head. There's no way in hell the stormtroopers are going to hit Luke or anyone else on the Death Star and kill them, since they're the heroes and have to make it out alive. The stormtroopers may be well-trained killing machines, brutal and efficient, and excellent marksmen, but it is the hallmark of Hollywood to make the enemy bad shots when they have to attack the hero. Only sometimes do they actually hit their target, and then it's only to open up some kind of dramatic scene, i.e. Han crouching over Leia at the Endor bunker and being ambushed by the stormtroopers.