Originally Posted by The Archangel
You're the one misunderstanding. Hollows do exactly that, they kill without thinking because they are evil, what you're talking about are arrancars, hollows that removed their masks and gained back their ability to think.
As such, they no longer randomly kill everyone they see and may even let some of their enemies live but that doesn't make them any less evil, in fact it just turns them into sadists that prefer to see their opponents suffer rather than finish them off on the spot.
They're still evil, they're just not brainless animals anymore