according to this [1], it's difficult to package them up and deliver them without harming them. if it was an easier / more lucrative problem to solve then surely it would be solved.
Not a very comprehensive list, but Mr. Sheehan's website has some information.
a quote from [1] :
'Food fraud can take place in many forms. A company might substitute one product for another, use additives or enhancements that are not approved or misrepresent the country of origin of the product. Stolen food shipments or intentional contamination of the product is also considered food fraud.
Food fraud is a continuum of deception. At one end of spectrum, there is the deliberate substitution of inferior and potentially harmful ingredients. At the other end is the mislabeling of common products by the largest food companies. The largest food companies will not engage in outright food fraud intentionally by using different ingredients that could be harmful. Instead, they typically would engage in a more subtle deception – all natural claims, no preservatives, healthy, yet containing lots of chemicals, etc.'