Behavior makes a lot more sense when you realize that humans are trying to have as accurate a view of the world as possible while also conserving cognitive resources. Running a brain is actually astonishingly expensive in terms of calories, so we've evolved to be judicious in how much thought we put into things.
Changing an existing belief is hard because we already spent effort acquiring the belief in the first place. Throwing that out should be expensive because otherwise we risk thrashing where we are constantly vacillating between competing beliefs. It makes more sense in terms of efficiency and being able to take action if there is some hysteresis and beliefs are sticky.
Note that while people don't change beliefs easily, they do acquire them pretty easily. If I tell you something that doesn't directly conflict with an existing belief, it's easy to absorb.
Changing an existing belief is hard because we already spent effort acquiring the belief in the first place. Throwing that out should be expensive because otherwise we risk thrashing where we are constantly vacillating between competing beliefs. It makes more sense in terms of efficiency and being able to take action if there is some hysteresis and beliefs are sticky.
Note that while people don't change beliefs easily, they do acquire them pretty easily. If I tell you something that doesn't directly conflict with an existing belief, it's easy to absorb.