Because if he does MSLSD and Joy Behar will scream "if that's not grounds for impeachment..."
But they're gonna impeach him anyway so he might as well do it.
The question implies the possibility, but I tend to think that if they had anything on him, they would have used it already. In whatever case, we can hope he declassifies them in 2021 at least.
The fact that Comey and company gave full immunity to Hillary and crew before they even asked questions or started investigation is ridiculous. The AG should direct the Dept of Justice to open an investigation into the Uranium One scandal and give everyone including all of Mueller’s victim’s immunity to those who will testify against Hillary and Mueller.