From the Tail: Betting on Uncertainty asks the question and suggests the answer is that humans in general have an aversion to uncertainty and accident. There is too little tolerance for ambiguity. And so the explicit randomness in evolution is too unsettling.
I would add: This aversion to randomness is one of the main reasons that religion still hangs around. People think -- not necessarily with real justification -- that life needs to have "meaning" and "purpose". And so a theory is unwelcome if it seems to imply that life in general -- and humans in particular -- might be just an accident. Instead, people crave a belief system that posits there is no uncertainty, no randomness, no lack of intentionality behind nature.
Even Einstein, famously, hated quantum theory because of its essential randomness. His (failed) scientfic quest was to find a few equations that required the universe to be as it is and not otherwise, so that ultimately even a deity couldn't have made things differently. Perhaps the main reason that religious fundamentalists haven't attacked quantum theory yet is that they know so little about it.
Of course, the aversion to the theory of evolution is especially intense in the U. S., and not all forms of religious belief are hostile to evolutionary theory, so further explanation is needed. Presumably the thrall to fundamentalist religion in which so many people in the U. S. are trapped must play a big part. But how to explain that? One needs to look at history and the tradition of anti-intellectualism in American life.
Other thoughts on these questions are here, here, and here.
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