In response to @V_'s post I've read Silo, not Hive Minds so I can only answer to what I've understood from Silo. There the well-off people are able to more easily attend the cleaning and eat in the cafeteria. There is status associated with living up top because you can look at the sky through the big video screen. There is no inherent danger from the outside so further down isn't safer per se. Of course the air is dangerous but they don't live in danger every day.