Lunch as the primary meal of the day is a staple of Mediterranean cultures. Italy, Spain, Greece, et. al., all have large lunches and small dinners. Latin America is also in many ways a Mediterranean culture so many Latin and Hispanic countries share in that trait.
In every university cantina in Spain you will find a multiple-course lunch. Better yet, (at least in Madrid) every institute has its own cantina, so you can decide between different lunch options: "Wanna go to physics today?", "No, I'll eat at the Ophtamologists".
Hot meals in he afternoon also were common in Western Europe, as is clear from the etymology of the word 'dinner' (via the French 'dejeuner' from the Latin for 'breakfast', which was eaten at noon or thereabouts) http://en.wikipedia.org/wiki/Dinner:
Originally, dinner referred to the first meal of a two-meal day, a heavy meal occurring about noon.
[...]
In Europe the fashionable hour for dinner began to be incrementally postponed during the 18th century, to two and three in the afternoon, until at the time of the First French Empire an English traveler to Paris remarked upon the "abominable habit of dining as late as seven in the evening".
I think it made sense to have a hot meal during lunchtime in places where the sun may set early at night because cooking in the relative dark would be more dangerous than cooking during daylight (swaying around a burning stick inside a wooden house to search for ingredients, spare wood, etc, is not a good idea)
As do much of England outside of London and much of the American Midwest.
English-speaking cultures use the word "dinner" for the main meal of the day whenever it happens. Cultures that eat breakfast, dinner, and supper have a large midday meal and a small evening meal. Cultures that eat breakfast, lunch, and dinner are the other way around. It just so happens that the English-speaking cultures that make more movies and TV shows (namely London and the coasts) are breakfast-lunch-dinner cultures, so people assume this is normal everywhere.
