I suspect the missing angle is that people are more likely to trust claims made to the public if, in principle, those claims could be verified by the public.

Of course it's pretty impractical that a bunch of concerned citizens might gather together and check the published data against how they each remember voting. But preserving the possibility in principle makes it easier to trust the published results. It gives a would-be deceiver yet another thing to worry about.

Its a trade-off I'd have opted into had I been asked. Though I'd feel a lot better about it if I had been asked.