What was sad about the case of the house owner? Who had his oak covered?

He also tells about a shop that boasts a beautiful carved oak staircase, which the present owner has covered in blue wallpaper. J. uses this as an occasion to meditate on how people always want what they cannot have, and do not want the things they do have. He recalls a former classmate named Stivvings, who was dedicated to his studies but was often too sick to complete his work. Meanwhile, the other boys hoped to get sick to avoid schoolwork, and became sick only when vacation came around. Returning to the subject of the oak staircase, J. writes at length about how people in the future will consider quotidian objects like dinner-plates and cheap figurines as priceless works of art, much as his contemporaries consider the day-to-day objects of prior civilizations to be priceless.