Because, after all, who is better qualified than the CIA to determine if emails of most of their staff, employees, spies, etc., can be deleted within three years "or when no longer needed, whichever is sooner." No, I'm sure nothing could possibly go wrong with that sort of retention policy with that particular agency.
The CIA wants to destroy thousands of internal emails covering spy operations and other activities
A CIA plan to erase tens of thousands of its internal emails, which has been tentatively approved by the National Archives, “could allow for the destruction of crucial documentary evidence regarding the CIA’s activities,” Senate Intelligence Committee members wrote in a letter to the archives. But agency officials shot back, calling the committee’s concerns grossly overblown and ill informed.
It's funny, but when I put together the phrase, "If you can't trust the CIA, who can you trust?".. I realize that the CIA is actually very near the bottom of the list. I think there would even still be room to trust the FBI and the NSA.