In some places that is a strategy to satisfy zoning requirements. The builder has to provide a minimum amount of outdoor area per dwelling unit. They could create a large ground-level courtyard, or they can create a bunch of tiny balconies that sum up to the same total area. The ladder latter strategy allows a larger building to exist on the same lot.
A different design other than a basic box would allow them to make a large outdoor area at basically any level they want, not necessarily the ground, but that's of course more expensive as well.
I think people value private outdoor space differently than public outdoor space. I don't actually have a balcony but I think I would usually prefer a private space to a public one, even if the public one was much nicer.
They don't really have to encase each floor. most buildings are concrete, and they could just as easily seal that floor off and leave the observation platform open. But the reality is that it gets pretty windy up that high, and most people won't want to be out there for very long at all. And not at all if it's at all inclement.
Personally, assisted suicide should be allowed; (but also maybe mandate a few rounds of therapy?) this way people don’t have to find out what being a human shaped puddle is like, because they jumped from not-high-enough.