What is the most ignored or underestimated component of Quality Management?

In my experience, suppliers tend to overlook the importance of packaging information.

What is, in your experience, the most overlooked or ignored part of quality control in your field?

I would say a quality plan is most overlooked. 

A lot of companies have the quality checks but don't really do anything with the data or make corrections on the production line. When you haven't identified the where and why these quality issues are occurring,  you can't train your operators on the how to make adjustments. Even for the SQF quality module, the score doesnt count against you, so it really is just a check box since its not required by law like food safety is.