It's superpowers lmao. It's just supposed to be a stun effect, not a master effect. It's practically magic, I'm not sure why it's so hard for people to wrap their heads around this. It's not like Vicky is the only person in all of fiction with a power like hers, yet I only here talks about long term effects with her, probably because the fandom's woobification of Amy.
It's like asking why doesn't Superman destroy the Earth when he reaches super fast speeds. It's magic, you're not supposed to think about it. You're only thinking about it because of Amy's woobification. (Some comics have explanations as to why Superman doesn't destroy the Earth, but my point stands).
Writers can write things, they can even come up with in-universe explanations as to why what the write makes sense even if it wouldn't in a normal context. That's the power of writing.
But if some people find those explanations unsatisfactory, or feel they invite additional confusion, people will break from the writers established cannon.
And I don't just mean unsatisfactory in a logical sense, where the A to B reasoning creates plot holes. I mean unsatisfying in an emotional sense. When fans feel like an idea was left unexplored, or would be more interesting than the 'logical' conclusion of the writer, well, that's fertile ground for fanfiction.
Wildbow left the matter of Vicky's power vague for a long time, both in Worm and his WoGs surrounding it. People drew conclusions about the effects of the power, then wrote what possibilities were created from those conclusions. Wildbow did not correct these people, and at this point I can only speculate as to why, but I would guess it would be because Vicky was not the protagonist of Worm, as such clarifying her power would have little impact on the focal point of the narrative. That focal point being Taylor, who only interacted with Vicky maybe a handful of times.
Then Ward was written. Vicky was the protagonist, and suddenly what her powers could or could not do became very important. Thus, Wildbow decided to clarify and explain Vicky's powers, incidentally wiping away all the possibilities created by the fans conclusions.
The explanation for this that Wildbow gave, that Vicky's emotional powers worked without negative side effects, was found to be unsatisfying by people who wanted to tell stories based around the possibilities. They found it to be logically unsatisfying, as it conflicted with a modern understanding of human psychology, even if the effects can be handwaved in universe. And/or emotionally unsatisfying, as it killed potential plot points and conflicts.
So people just... Went on to write those plots anyway.
Fanfic writers can justify it different ways, call it an AU, call it a reasonable deduction or realism applied to superpowers-
But at the end of the day, Vicky's powers being a simple stun effect doesn't create nearly as many potential stories as the more complex and messy explanation.
To tie things back to Brockton Bay's Celestial Forge. The entire plotline about Amy's master-stranger confinement, and the vast web of knock-on effects from that such as the New Wave team breakdown, the tightened protocols on Joe, Mark showing up-
It all stemmed from Vicky's powers messing with Amy's head and triggering a master alert.
If you like those plot lines? Then you're probably in favor of this interpretation of Vicky's power, as it's required to tell these stories in this manner. If you don't like these plot lines? Then Vicky's power being as Wildbow enforced might appeal to you more as it takes the legs out from under those aspects of the story.