"If men are to be saved, the enemy is reason." -- Ayn Rand
That is essentially correct. The precise answer is that men do not want to know the truth. Here is a longer explanation from some pages I have abondoned. This section was written to answer the question of why men are universally superstitious.
A Secret Loathing
Reality is ruthless. Defy reality, and it will destroy you. Refuse to work, and you will starve. Refuse to learn, and the mistakes you make in you ignorance will kill you.
Reality is demanding. You must conform to the nature of reality all the time, because the moment you let up, it will strike you down. Stop paying attention, just for a few moments, while driving on the highway at 70 miles per hour. Don't bother paying your bills for a month. Forget you insulin injections for a day. Just forget where little Sarah is for a while at the Mall.
Reality is cruel. Disease, death, disaster strike without regard to anyone's position or opinions. The world is full of destruction and misery, though most of it is created by other men. But all of nature is cruel and the entire chain of life is one of death, killing, and being killed.
Reality is unforgiving. You've made a mistake, but the law forgives you, your parents and friends forgive you, you even manage to forgive yourself, but reality never forgives. It may be a forgivable mistake, but the dead animal cannot be made alive again, the pregnant girl cannot be made "unpregnant", (at least she can never have her virginity restored,) you cannot cancel what you have done, never! Have you been unfaithful once, then you will always have been unfaithful once. Did you steal something once, then you can never claim always to have been honest. You do something stupid and loose an arm, leg, or put our your own or someone else's eye. You may never do another thing so foolish, but you will never have the arm, leg, or eye, yours or another's, restored.
While it is true that reality is ruthless, demanding, and unforgiving, cruelty cannot really be attributed to reality, even though all the things listed as cruel are true in nature, the evaluation of them as cruel is a subjective judgement. This characterization of reality is only a partial view, the view of one whose knowledge is primarily irrational and superstitious.
It is this view, though seldom made explicit, that is the motivator for our mysterious factor, the cause of universal superstition. Mankind, generally hates reality, just because mankind does view reality as ruthless, demanding, cruel, and unforgiving. What mankind wishes for is a reality that is pliable, easy-going, kind, and forgiving. At bottom, mankind hates reality, hates the necessity of having to work hard all the time, hates the necessity of having to learn so much, hates never being able to act on whim, or passion, or impulse without consequences, hates knowing they cannot do wrong and get away with it, hates knowing you cannot get something for nothing.
What mankind wants is exemption from consequences and a shortcut to success, wealth, happiness, or whatever else their current whims and fancies convince them they want. Reason does not show them how to have or achieve what they want the way they want it. Reason only enables them to understand the truth that describes reality as it is. They don't want truth, either. The truth just condemns them for their hate of reality. They hate the truth, too.
Here, finally, is the secret, that unrevealed factor, the mystery of why almost all men prefer their superstitions to the truth.
At the heart of all superstitious beliefs, sometimes explicit, but always implicit, is the promise that there is something more than reality, something above reality, something which cancels the requirements of reality, a secret that enables those who know it to rise above mere reality, to defy it and get away with it. Superstition, which is never called superstition, is a magic wand that makes exist what in reality cannot exist, a metaphysical wild card that makes one automatically a winner, the universal "get-out-of-jail-free" card that allows one to escape the consequences of their choices and actions, the flying carpet that defies all of reality to give its owner a free ride to success and happiness.
Men hate reality and the truth and will accept anything that let's them believe they can escape it.
Hank