Because she's not a sociopath? I'm pretty sure I covered it with "even though she has the power to do so at no cost to herself and with trivial effort." "Why should people not stop horrible things that upset them when they can do so trivially?" seems like a pretty disingenuous question. The manga actually trys to address this in the last chapter of volume 2 where she has a wee cry about it and her master gives her some super unconvincing rhetoric about how its fine to be totally passive and that witches dont have any power - even though literally every time we've seen magic used it completely undermines that viewpoint. Look, if she's a sociopath fine. But the way its handled undermines my suspension of disbelief and robs the story of any real pathos for me. Which is why I was complaining about it. If you feel different then, genuinely, good for you. I'm not trying to convince people to adopt my viewpoint, simply expressing it.