Although tireless efforts have turned up nothing illegal or terrifying about Clinton's email usage, maybe releasing ALL the evidence will shut up the obsessive conspiracy theorists. These paranoid theory-crafters, however, have already gained access to a wealth of evidence that has costed the taxpayers a ton of money. Why not release every document to try and put the issue to rest?
If the scandal with Hillary Clinton's email was that she sent classified information over a non-classified channel of communication, I am unsure what benefit would result in public exposure of those documents. If the emails contained items concerning national security, then I believe releasing that information could be more harmful. If the information is against the citizens of the U.S. then perhaps exposure is valid.
No, the public does not need to know every detail regarding Hillary Clinton's email evidence. The FBI has a job to do and needs to investigate thoroughly. It does owe the public the final results of its investigation. However, it does not need to release every single detail of the case.
There has been so much controversy and so much media attention surrounding the emails that if the FBI were to release them to the general public, it would only have a negative impact by causing people to bicker, fight, and argue and get absolutely nothing done and reach no helpful conclusions. It would be a pointless, political ploy to distract people from the real issues and cause needless unrest, regardless of the content of the emails.