I suppose the answer is that most people are simply intellectually lazy. It is so much easier to accept what some ancient sage/tradition/book says than it is to actually think for oneself or to scurry around and find real information.
When combined with the popular distaste for science, which likely also comes from laziness, you get the current enthusiasm for old guff.
It doesn't help that there are all kinds of hucksters such as "alternative medicine" gurus, pastors etc making a good living spreading the guff.
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