Children often need a snack between meals. They cannot take as much food as adults in one sitting and their energy needs are higher, so they need to eat more often. It is invaluable to have always something wholesome at hand.
Kids seem to be always hungry. True, children need to eat little and often; little because they don’t have much room to sink the food in, often because they are still growing and their need for energy is higher, compared to their weight, than a grown up person.