Just speculating here, but maybe because of false positives where flu cases get labeled as Covid? I've heard that PCR tests were not meant to be used for large scale virus detection. EDIT: The PCR test quote was fact checked and deemed to be misleading, but it still sounds like they are not very accurate [0]. [0]: https://www.reuters.com/article/uk-factcheck-pcr-idUSKBN2442...
What in that link sounds "not very accurate"?
The fraud is not in the test itself, but in the reporting of test results. When a PCR test comes back positive, more often than not it is assumed the patient is infected with COVID (which may not be the case) - and cases of infected people are reported widely using these PCR test results.