Plenty of people go their whole life never thinking of challenging the claim, of looking to verify it. The thought never crosses their mind.

Do you have any evidence that this is the case? In my experience, it's not. Most people tend to feel that coming up with an argument for why their particular beliefs are true is extremely important, it's just that they then fall into patterns of confirmation/disconfirmation bias, affect bias, and mind-projection fallacy. A person raised in a fundamentalist Christian home is taught that there are really true and verifiable explanations for the specifics of why evolution is wrong. There's a huge propensity to find ambiguity intolerable. The more dogmatically an assertion is held, the more intolerable ambiguity becomes.

The cases where error exists due to sheer lack of curiosity don't appear to be common. But in those cases, maybe a more fundamental question to ask is why there is a lack of curiosity. Perhaps it is social convention to accept an idea and it would be uncomfortable to challenge it. Perhaps adherence to a particular idea has provided a reasonable amount of comfort and consistency in a tribe's history and if they cannot imagine increases in their success and comfort, there is little motivation to stray from the accepted dogma. These types of question cast light on what this sort of mistake is, which is different from hypocrisy/akrasia. I'm just not sure this question is (a) an important distinction or (b) worth adding on to this particular thread. It might be worth creating a new discussion thread for it though, to get more thoughts than just my own.