I figured it was because society is so far removed from being healthy, that people are experiencing low grade versions of de-personalization. We are way beyond the dunbar number, forced to make humiliating compromises for no benefit to ourselves, and there is little we can do to minimize the stress of it. We fantasize about zombie apocalypse because it is in someways "better" than modern life. In past ages, over population would lead to splitting of a population and geographic separation, if the group ejected met rivals on the way to a new home, the result would be a desperate fight for survival not unlike those movies.