People are predisposed to form ingroups and outgroups. The higher the price of admission to an ingroup, then generally the greater the loyalty to that group because after all, if the member paid a high price to join a group that didn't deserve loyalty that would mean the member was pretty stupid to join. Instead of admitting they were stupid many people increase their dedication to the group instead. In the old days admission to a group may have involved a physical ordeal or initiation rite, but today the price of admission is more likely to believe in something outlandish or magical. The best examples of these groups are those that believe in the existance supernatural beings.