CIA JFK Files - Exciting But Frustrating

Thousands of CIA files related to the murder of JFK apparently with CIA involvement has been released.
Researchers are both excited by the release of so much information but also frustrated because it seems much is still missing. Why are events six decades ago still a "national security risk"? Sounds more like criminals trying to avoid prosecution and being barred from running the nation behind the scenes with such disastrous results and looming bankruptcy of the federal government.