Why Did the Chicken Cross the Road?

Why did the chicken cross the road?

Examples (this is stolen directly from Rachel's email):

Dr. Seuss
"Did the chicken cross the road?
Did he cross it with a toad?
Yes! the chicken crossed the road,
but why it crossed, I've not been told!"
Karl Marx
"It was a historical inevitability."
Ernest Hemingway
"To die. In the rain."
Bill Gates
"I have just released eChicken 2000, which will not only cross roads, but will lay eggs, file your important documents, and balance your checkbook -- and Internet Explorer is an inextricable part of eChicken."
Ronald Regan
"What chicken?"
Captain James T. Kirk
"To boldly go where no chicken has gone before."
Sigmund Freud
"The fact that you are at all concerned that the chicken crossed the road reveals your underlying sexual insecurity."
Einstein
"Did the chicken really cross the road or did the road move beneath the chicken?"
Bill Clinton
"I did not cross the road with THAT chicken.
What do you mean by 'chicken?'
Could you define "chicken" please."
Martin Luther King Jr.
I envision a world where all chickens will be free to cross roads without having their motives called into question.
Richard M. Nixon
The chicken did not cross the road. I repeat, the chicken did NOT cross the road.
Jerry Sienfield
Why does anyone cross a road? I mean, why doesn't anyone ever think to ask, what the heck was this chicken doing walking around all over the place, anyway?
Darwin
Chickens, over great periods of time, have been naturally selected in such a way that they are now genetically disposed to cross roads.
Ralph Waldo Emerson
The chicken did not cross the road....it transcended it
Sir Isaac Newton
Chickens at rest tend to stay at rest. Chickens in motion tend to cross the road.
Thomas Paine
Out of common sense.