Humans seem to gravitate toward certainty and consistency the way moths fly toward light. It's an emotional craving, and in order to be rational we have to be exceedingly comfortable not knowing things (and realizing we often don't know what we don't know).

The more a person seeks the opiatic, emotional feeling of fake knowing, the more receptive he is to religion, political brainwashing, conspiracy theories, prejudices, social authority structures, etc.