People are bad at reporting ANYTHING. Exercise, food, sex, grooming. Just ask a lawyer or anybody trying to get a story out of somebody. This should be a fundamental understanding of anybody asking people anything. That scientists imagine there's some accurately-reporting population of subjects for their experiment is an example of the breathtaking naivete of scientists.
Crows are never whiter by washing.
You cannot dispense common sense through the educational system. Most career scientists are mediocre, and/or they are trying to survive in a rigged system.