Why do so many people nail thier own coffins?
Let's plat out a scenario:

You are on a plane and it is a long flight. There are no windows, and you are convinced you are only five feet above the ground, even though there is no way to tell. You know that eventually, you will jump out of the plane, but your not sure exactly when. The stewardess comes to you and says "Would you like a parachute?"
"No thank you, the ground is not far."
"But sir... when you jump out you will need it... We are 50000 feet up..."
"No thank you, I say! Prove to me we are high in the air, and I will take it!"
"But it's free... you don't need to do anything, just..."
"Stop pushing your parachute on me!! I said no!!"

The stewardess walks away confused. You are proud that you have sacrificed your parachute to assert that without scientific proof you were in the air, you would not be convinced.

Eventually the time comes to jump out of the plane, and as your falling, you realize you are much farther up than you had thought, and wishing you had a parachute but it is too late now.

This makes no sense right? Then why do atheists make this decision every day?