It is estimated that 1% of the population has celiac disease: an autoimmune condition that flares in response to eating gluten; the protein found in wheat, rye, barley, and triticale. As it is, people with celiac disease are forced to consume only products from a very limited, overpriced set of options where the manufacturer chose to test and disclose that the product is is gluten-free; make everything from scratch; or take their chances.
With celiac, consuming gluten is not immediately life-threatening - but it is painful, and it can cause life-threatening complications, from nutrient deficiency due to malabsorption, to intestinal cancer. A simple change to food labeling would make eating much safer for people with this disease and save money in healthcare costs for complications.