In the 19th century, when a lot of these buildings were put up, the poorest people lived on the top floor. That's because there were few mechanical elevators and getting up there required an arduous climb. What a good deal for the poor! They not only got a terrific view of the city but they were able to look out over the surreal, mysterious, innovative, historic, artistic wonderland of the rooftops!
Some rooftops seemed to be planned and ornate, others seeme to be gerry-rigged and put up almost as an afterthought. Maybe some featured add-on rooms, built without knowledge of the law. Some of the most creative designs might have been add-ons.
Rooftops like these provoke so many interesting questions. Are we wasting the best part of buildings by putting them so high above the street that nobody can see them? Should we build rooftop-type structures on the street level? Should we promote a world above the ground by bridging rooftops? Should we deliberately send our eccentrics up there to live in the hope that they'll create an interesting world up there? Should we have trolleys up there so rooftop people could visit each other without going down to the ground?
Matbe witches or Dickensian criminal types like Fagin should live up there. Maybe ninjas. Maybe thatched cottages and trees should be permitted. Maybe a foreign country should be allowed to exist up there.