One of the many reasons I encourage my clients to eat 6-9 servings of veggies a day is because green veggies are a high-volume density, high-nutrient density, and low-caloric density food. Higher food volume create better satiety and fullness, without the negative consequences of more super-palatable foods like Rx bars or ice cream, where a very small amount of food volume packs a caloric punch with relatively less nutrients.
The only time we would have experienced a super-palatable food in nature would have been honey, and by no means was that a daily occurrence. Don’t get me wrong, super-palatable foods have there place and are delicious. But if you want to operate at a slight calorie deficit without feeling hungry, strive to consume 2-3 servings of veggies at each meal.