UFOs are the next war on terror. The government will create $89859858 trillion to fund the development of weapons if an alien invasion ever happens, and we'll get the Patriot Act 2.0! It's genius!

We'll search for WOMD forever, and ever, and ever, and ever, and ever, and ever, and then tell everyone they have to work for free because all resources have to go toward preparing for the invasion.

This is the only logical explanation I've come up with.