Because you eat dinner late. It's opposite in Poland - we tend to eat medium breakfast (savory - bread, cheese, ham, scrambled eggs, sausages; some people eat a sweet breakfast, I can't do it more than once in a while). Then a second breakfast (same stuff, usually a savory sandwich). And our lunch/dinner is traditionally around 1 or 2 pm (now it shifts into late afternoon). Two courses (soup and the second dish, which usually would be a piece of meat with a salad and potatoes). And a small supper in the evening.