With the advent of the Enlightenment came critical thinking and more importantly, the scientific method, which worked so well at explaining physical reality around us that "myths" became essentially discredited as explanations for the way the world worked. As a result, the word "myth" eventually became associated with "lie" (even though the two terms were originally unrelated); we still occasionally use the word "myth" as an alternative to "lie", in fact.
Stephen Hawking basically said the same thing in a "nice" way when he suggested that whether or not you believe in God, it is not a necessary part of the puzzle to understanding trhe universe.
Randy