Why do we eat certain types of food for breakfast, lunch, and dinner?

We eat 'breakfast food' for breakfast, 'lunch food' for lunch, and 'dinner food' for dinner. Why is this? Hamburgers are healthy, why don't we eat them for breakfast? Whole wheat cereal is good for you too, why can't we eat that for dinner? Has this way of life just been ingrained in us for many centuries? Or is there some reason for this behavior?