Obviously not a perfect equivalency, but Vader cuts down dudes with the lightsaber for the same reasoning The Emperor ever bothers to use lightning. Not as quick or efficient, but it allows these awful people to revel in their hatred and bloodlust. That’s the dark side operates. Vader’s also not entirely concerned with getting back the readouts to the technological terror the Empire has constructed, nor did he realize how close he was to them. Which isn’t nearly as damning of foresight when you compare it to staring your own daughter in the face and not realizing who she is. But hatred gives you tunnel vision in the Star Wars universe, I suppose.