(CBP/BP) Failure Rate

[Flabbergasted]

I'm part of the majority that failed a CBP/BP polygraph examination.  The standard story that others have experienced applies here, with the exception that my examiner took a cold and calculated approach rather than being openly hostile or rude.

My question is not what happened, as that's been answered thoroughly on this site, but why.

CBP/BP have well-known ongoing shortages that are impacting security and supply chains, so why are their polygraph examiners still failing the majority of those who sit for the polygraph?  Is it as simple as them justifying their jobs?