Lots of people find it easy to be "nice" to others when there is nothing on the line - no money, no reputation, nothing at risk. Why say something critical and create bad feelings when you gain nothing by it? Surveys and market research get skewed for this reason.
You always get more honest and accurate feedback when you actually "ask for the sale". It doesn't even have to be a literal "sale", it could be a change in a policy, as in the story above.