Why do so many seemingly intelligent people believe in astrology? Or homeopathic medicine? Or acupuncture? Or chiropractic “medicine”? Or any other system of beleif with no rational basis in fact?
Answer number one is, I think, the power of tradition. People believe in things because that’s what they were raised to believe. Peer pressure also forms a part of this answer, since people in general like to fit in with those around them.
Answer number two is, I think, a deep-rooted, perhaps even innate need to be able to explain the unexplained. For some people, this leads to a life of philosophical and/or scientific Inquiry. For other, it leads to a growing sense of credulity wherein thay are predisposed to believe anything that purports to explain the otherwise unexplainable. And, sadly, these two paths are not mutually exclusive; one can be a serious student of science and philosophy and still be suckered into believing one absurd notion or another.
Answer number three is, I think the nearly overwhelming power of anecdotal evidence, especially when experienced first-hand. Logical analysis, the scientific metod, and the doctrine of falsifiability are all well and good, but they often take a distant back seat to emotion when a person experiences (or knows somebody who experiences) what he or she believes to be “proof.” Sure, there’s no rational explanation to believe that homeopathic medicine could possibly be effective, but tell that to the person who suffered from sever hayfever for years until drinking a “magic elixer” and being “cured.” It doesn’t matter that many other people have not been helped or that there is no possible way in which the explained cause could have had the observed effect. Similarly, religion is full of so-called “faith promoting stories” that provide irrefutable “proof” of the existence of God to those willing to chuck logic and rational thought out the window.
Then, of course, you’ve got to consider the fact that religious beliefs provide comfort in the face of loss and pain, provide the weak and helpless with a sense of superiority over the strong and successful (in this life, of course), etc.