Religion is the opiate of the masses. Meaning, of those who go to mass.
Ha. Ha. Haaa.
Anyway. I was thinking of Hans' comment, and considering why religion is so prevalent in the world. I came to the conclusion that it's primarily based around sticks. Christianity, for instance, has a big, flaming stick - hell. Were there a religion that did not have a stick or a carrot of some shade, no one (or rather very few) would believe in it. They get nothing out of it. They do not get punished for incorrect practice, or rewarded for an accurate observation of its tenets.
So, with that in mind, religion is so prevalent because mankind is greedy and scared. Though, in kinder light, 'greedy' may be reinterpreted as 'hopeful'.
The above thought then led to how Christianity managed to survive in the religious melee. I came to the conclusion that Christianity has both a juicy carrot (heaven, loving daddy, being able to meet all the dead people you love, and immortality) and a big stick (hell, estrangement from the loving daddy, a barring from seeing loved ones, physical torment). It also says that man should spread this religion, but as this is parsed in terms of reward and punishment it need not get a separate heading. This led to its adoption and its observation. It led to Children being born into it and being told that it is truth. Other, less reward-focused doctrinal systems fell by the wayside because they did not have a clear message surrounding what the practitioner can gain and what they may lose.
My two cents and all that. Still, I can't help but think of religion in this light. A system which subsides on the fear and greed of humanity. It is no wonder that when people perceive the Bible to tell them that the world is flat, then they believe it despite evidence. To do otherwise would invite falling pray to the stick and abandoning the carrot.