Most of these aliens that visit earth (and I beileive the list is up to 8 species as far as the government's got listed) don't travel at NASA shuttle speed. We could get into a whole "folding space" and "extradimensional beings" talk but it's late and I'm feeling sleepy and don't want to bore everyone esle.
Because people are idiots. Duh
I've actually made a few tin foil hats myself and worn them around just for shits and giggles. The whole tim foil thing is basically a mockery of UFO believers.
Would now be a good time to bring up that I've seen 6 seperate UFO's (in 5 seperate experiences) in my time starting at age 5?
The physical evidence of the UFO phenominom and aliens on Earth are just to extensive to say it doesn't exist.