Because the state department report as well as the FBI investigation have not established guilt or that they have enough to charge her with.

At the moment the most they could charge her with is breaking FOIA, which is a crime with no punishment.

U/imperiyo is mistaken or deliberately misleading some of the facts.

Example would be "Clinton declared under oath to a Federal judge that she had given all her emails to the State Department" when this is not accurate. She declared under oath that she had given all her work related emails to the state department"

another example "Federal crime of negligence with classified information and documents " he is representing this as a black and white case law area where that is not the case at all, plus he is implying that these are the same type of classified documents that are on the State Departments Closed Classified server, they are not.

Another is the "1,200" secret document, most of them were reclassified after the fact, which is standard operating procedure during a FOIA request. Most of these were reclassified at the FBI's request so as to no hurt public relations with whatever country's diplomats they may be from.

In other words. Gross Negligence is extremely hard to prove, and as of now they can't prove it.