If we're talking Storm Troopers, they were never intended to kill Jedi....I mean they are a front line of defense but they haven't a prayer against OP space wizards that can drag an entire enemy armada from the sky with just a thought. Those things are for killing droids and regular soldiers and mercs and shit like that. Not Jedi other than on a fluke.
So if you're waiting for a Storm Trooper to ice Luke, then that's gonna be a tall ass order.
Kinda why in the midst of it all, only Jedi kill other Jedi for the larger part.