I've seen places where the roof is an outdoor living space. That is the stairs go up to the top (not just maintenance access, but full access), and there is a

I've seen places where the roof is an outdoor living space. That is the stairs go up to the top (not just maintenance access, but full access), and there is a safety railing around the top so kids can't fall off the edge. They are a great place to have a party, and replace the suburban backyard. That is the primary benefit of a flat roof, but it is only a tiny number of buildings that are like this. The vast majority of buildings do not allow roof access. Still I encourage it.