Area 51 is the most secure military installation in the world. This is because underneath the base is a D.U.M.B. (deep underground military base). Inside that D.U.M.B. is some of the United States most valuable technologies. Some of which are military weapons, chemical agents, and even test labs for thereof.
Scientists and personnel are flown, and bused in each day for work with the utmost security. This is because the stuff they produce down there won't see the light of the private sector for at least 10 years. (if at all)
To be honest I don't think there is a UFO inside area 51. Although I don't doubt there could be. I think that the Roswell crash was just a hoax conducted by secret organizations within our Government. For the intentions to create a place like "Area 51" where no citizen can go. Even congressmen, and senators have been denied clearance to this place. It is literally a place that doesn't exist.