For the usual reason, Nation Security.... What they do with the above top secret is to give them to corporation and not a government office that way there is no way anyone can ever ask for info or data on it. It's privately owned by a corp that is run by a shadow government.
Check out this below, it talks about that a bit and other interesting stuff:
Linda Moulton Howe - MUFON
In the mid-1990s, filmmaker and researcher Linda Moulton Howe was approached by former New Mexico State Representative Andrew Kissner. He shared with her his official and off-the-record research concerning the 1947 Roswell incident and other alleged UFO crash retrievals in New Mexico. Rep. Kissner had assembled many old newspaper articles and leaked government information from unofficial military and intelligence testimonies. He asserted there was an American government policy to shoot down unidentified discs in the late 1940s to early 1950s until retaliation by the discs, which included the deaths of many pilots, forced a cancellation of our aggression.
According to Howe, Rep. Kissner contends that the Truman Administration ordered a policy of denial in the interest of national security about all UFO crash retrievals, a policy that remains in force to this day. Howe will present information about the possible nature of the disc retaliation and other disturbing phenomena linked to the non-human intelligence controlling the discs.
Linda Moulton Howe is an Emmy Award-winning TV producer, investigative reporter and author. She graduated from Stanford University with a Masters Degree in Communication, and has devoted her documentary film, television and radio career to productions concerning science, medicine and the environment. With cutting-edge investigations into scientific anomalies like animal mutilations, crop circles and UFOs, Howe has also captured a spot at the forefront of the para science research community. In addition to her numerous professional and academic awards, Howes website,
http://wwwEarthfiles.com, also received an Encyclopedia Britannica award for internet excellence in June 2000 and the WebAward for Standard of Excellence in 2003
http://www.youtube.com/watch?v=5LDrGrsVp8Qhttp://www.youtube.com/watch?v=A_D1glnyclg
