I think whats been said is true for the many of belief systems people have.
For example ..
Believing the your government works for your best interests.
Believing that your superannuation funds (401k for Americans) are safe.
Believing that spouse could never cheat on you.
These are all held strongly in place ... until it has obviously fallen apart.
Its just a weakness that most people have, to default to a pattern of ignorance, because its easier (mentally, emotionally, physically and financially) than planning for a bad outcome.