You can have categories without loyalty, but groups can't exist without loyalty. We scrounged through the psychology and popular literature but found durn little in the way of studies of loyalty. Groups, he says, tell us who we are. Our identity comes from the group. We're often evaluated according to the group we belong to.
Groups are important for protection and social support.
If you need something, you may have to rely on the group. If you are attacked or threatened, you have to rely on the group. Obviously, some groups attract stronger loyalty than others. The question of increasing loyalty becomes critical to army recruiters, sports promoters and corporate brand managers. Dependent as they are on loyalty, groups must not just foster loyalty but also discourage disloyalty.