It's the same reason a dog licks his privates....because he can, and his owner lets him in front of God and everybody.
Yes, Hur is the dog, fully unsupervised by his Master, Garland, and Garland doesn't mind the public watching his dog lick its privates.
Hur is fully unqualified to make any psychiatric diagnosis, but as a trained attorney, he can probably notice when a deponent has short and long-term memory issues based on the line of questioning during a deposition and how the deponent responds. This includes redacted responses from the printed transcript, mumbling, and 'inaudible' answers. We all need to hear that raw deposition.
Since Brandon was questioned on his behavior and abuse of classified documents when Brandon was a Senator, Vice President, and a private citizen, and since the transcript has already been released, Brandon has no standing to impose Executive Privilege to hide the audio of his deposition s8nce he was not President during the bulk of his criminal activity as confirmed by Hur.
Now, Garland is watching his other dog, Brandon, lick his privates in public and lacks the balls himself to stop the rude behavior.
:: How does Hur get to make that determination ? ::
Because “no reasonable prosecutor would bring charges” was already used.