While it may seem contradictory at first, the appearance of low ability amongst credentialed candidates also lowers the perceived value of the non-credentialed; fore if the credentialed are so lacking in ability, then those unable to achieve even such a low bar must be worse, yes?
Of course, this isn't always true. But for hiring managers dealing with an insurmountable mountain of candidates any generalized filtering metric, however shaky in its footing, is appealing.
Widespread cheating is part of why we have credential inflation.