All  those rich people buying into underground complexes with completely  separate living quarters, restaurants, hospital, gaming rooms,theaters,  etc are also paranoid about what's going to happen once they must go  "below ground". Will their providers and  their security forces stay true to their contracts and promises of a  friendly, safe and secure environment for the elite,away from the  rioting mobs above ground? 
Or will they find themselves  double crossed, robbed of all their assets and thrown outside to those  very mobs they're afraid of and trying to escape. 
Greed brings with it paranoia. The greatest fear is being penniless and without the power of the fortunes. 
But,  take a real look at tribal living and you'll see a much better and  safer option for those who are willing to accept the work involved and  recruit and select the appropriate members to form a cohesive village or  tribe. Whether above or below ground, a like minded group of  individuals could actually have better chances of survival,  thriving  together and still possessing their freedom and individuality. - Robert Nuckles