The tonneau cover is usually there because A) they do mostly highway mikes and want the improved mileage resulting from reduced drag, and B) they rarely use the bed, as those covers are a PITA unless you only remove it once in a great while.

I live in Central America where its mostly little trucks owned by workers, and they often drive on mud roads and hard terrain. The only people with trucks like the black one in the picture are US expats with …particular political leanings.