Probably because foods labeled “diet” usually don’t taste very good. And, it usually costs more than the same food that isn’t labeled diet. Why buy “Weight Watchers approved” pop corn when you can make your own without the endorsement? When you called your burrito a “diet burrito” it implies that something yummy is left out. (I make burritos at home the same way. Sour Cream has no business being in Mexican food.)