Why do we categorize food by when we eat it?

For example, foods like scrambled eggs and oatmeal are labeled as “breakfast food”, and foods like soup and sandwiches are labeled as “lunch food”. What started this division of food? Why is it the norm to have orange juice for breakfast, but not for dinner? Why does McDonalds only offer McGriddles for breakfast?

I have a dream, that one day all foods will be treated equally.

I know some of you go against these norms, I do as well, but that’s not the point.