(The reason for this decision is not because they don't believe in aliens, but because they get so many calls. The problem is the calls aren't because there are little green men invading, but because of Chinese lanterns; people spot them flying around spookily and think they are UFOs, which I guess they are really, because UFO simply stands for Unidentified Flying Object, and so it stands to reason that if you see something flying around and you can't tell what it is, then it is de facto a UFO.
Maybe Chinese lanterns are a cunning alien plot?)