Bigfoot don't leave crop circles, either.
Do aliens?
"The phenomenon itself was observed in its current form after notable appearances in England in the late 1970s. Various explanations were offered for the phenomenon, which soon spread around the world. In 1991, two men named Doug Bower and Dave Chorley revealed that they had been making crop circles in England since 1978 using planks, rope, hats, and wire as their only tools.[1][2] Circlemakers.org,[3] a UK-based arts collective founded by John Lundberg have been creating complex crop circles since the early 1990s.[4]"
And
"The storms about this part of Surrey have been lately local and violent, and the effects produced in some instances curious. Visiting a neighbour's farm on Wednesday evening (21st), we found a field of standing wheat considerably knocked about, not as an entirety, but in patches forming, as viewed from a distance, circular spots....I could not trace locally any circumstances accounting for the peculiar forms of the patches in the field, nor indicating whether it was wind or rain, or both combined, which had caused them, beyond the general evidence everywhere of heavy rainfall. They were suggestive to me of some cyclonic wind action,..."[7]
Although the pixie circles said to be created by Elves in Scandinavian folklore were most likely caused by fungus colonies, there was also a rarer kind, consisting of circular patches where the grass had been flattened:
On lake shores, where the forest met the lake, you could find elf circles. They were round places where the grass had been flattened like a floor. Elves had danced there. By Lake Tisaren, I have seen one of those. It could be dangerous and one could become ill if one had trodden over such a place or if one destroyed anything there (an account given in 1926, Hellström 1990:36)."
http://en.wikipedia.org/wiki/Crop_circles
I've only met three people claiming UFO sightings. One lived near an Air Force base and was in early recovery from alcoholism and addiction, one probably saw a weather balloon caught in an updraft and one said himself a launching occured that evening.
I believe people see things in the sky, and sometimes on the ground, that baffle them, but I've met a grown man who didn't know the difference between stars and planets. I wonder what they teach in science classes these days - anything about what a light year is?
On the other hand, we have what seems to be a perfectly normal large bipedal primate, largely nocturnal, living in areas that are rugged and mountainous and forested where hikers and hunters and mushroom pickers get lost and die before anyone can find them, even though it's known where they were last seen. No warp drives necessary, no need to suspend natural laws to accomodate a belief system.
Why do I believe one and not the other? It's easier.