If the chance of hallucination could be statistically guaranteed to be near 0, then it would have many more use cases, imo... but why would I have it summarize

If the chance of hallucination could be statistically guaranteed to be near 0, then it would have many more use cases, imo... but why would I have it summarize a pdf or write some complex code or something if I have to always double check everything for accuracy? A calculator has no use case if it might be wrong.