Buildings that breathe
You breathe to live, and to feel comfortable in a building, the building must also 'breathe'. Unfortunately in most modern construction, air (and light) are not given the consideration they deserve. Too many builder-designers ignore passive ventilation and natural lighting and rely on mechanical ventilation and artificial lights. So it makes sense to place a vent in the floor of the shed, to draw in air from underneath, to take advantage of the cool shade there.