I always wondered what the additional parts were for too. The bridge parts made sense, but it appears the air hoses only apply to the 2-rail version of the car (or for owners wishing to convert the 3-rail car to a 2-rail version). Since the 3-rail version has a different coupler with built in brake hose detail, this part would not be needed.
Atlas O Coil Car (2-Rail Version)
Atlas O Coil Car (3-Rail Version)
-John