The purpose of peer review is not to uncover fraud.

And this is OK if the fraud rate is low, and unacceptable if it's high.

If a paper shows all its working, a competent reviewer can judge whether the work as reported is good. How will they detect that the report is a fabrication? All the reviewer sees is the story the author is telling. The reviewer may notice inconsistencies, such as repeated use of the same figures, or data with an implausible distribution, but they will generally have no way to compare the story with the actual facts of what happened in the lab.

Detecting and preventing fraud is a good thing, but I don't think peer review is a place where much of it can happen.