Breakfast cereals benefit from powerful marketing techniques, especially aimed at children. And of course kids love them because they are positively brimming with sugar.
Add to that the refined grains, artificial coloring, and chemical preservatives, and there is little nutritional value there, even if the box declares it is “fortified.” Regular old oatmeal sprinkled with nuts, dried fruit, or honey can be much more filling and keep you going strong until lunch as well.