Because the government is so determined to keep it secret. Not just legitimately secret tests, but things like refusing to confirm the base exists (when it's easily visible from a number of publicly accessible vantage points). When the government acts like that, people are driven by a combination of curiosity, paranoia, and well, basically trolling, to find out what's there. Honestly, if they'd just said what everyone knew--we test secret planes out there, please stay away or we will take action--they'd probably have less of a problem. But when the response to "What are you doing at that base?" Is "What base?" when it is obvious that there is. In fact, a base then you're pretty much inviting conspiracy theories.