It's hard to understand given HR's belief in the infallibility of their process but as true as the immutable laws of physics.
If you think conceptually about the role they 'fill', HR is really irrelevant.
They have invented a role, invented relevance and wedge themselves where ever they can; creating conflict where there is none, complexity where it isn't needed and inventing jargon to
'support the science of their endeavours'
There is little 'science' and less relevance...to them controlling a recruiting process ensures their own survival!