Nietzsche (him again!) was of the opinion that most people, not to say the vast majority, do not have an intellectual conscience, i.e. a desire to understand the world.
The question remains whether this is due to literally not having the ability for intellectual understanding or not exercising said understanding by putting it into daily practice.
This in turn raises the question of ignorance, defined as choosing to ignore what one can reasonably be expected to know, the information being widely and freely available (as well as accessible).