It's a power fantasy. There's an "in group" and through various mechanisms, it's perceived to be a concentration of power. Some people want to be on the right side of the line, while others actively distrust any organization that advertises the power fantasy behind a hidden agenda, or think it's childish, or both.

My view is that there's no harm in indulging this power fantasy if it's just a game, but when you try to merge it into your everyday life, you're playing with fire. Secrecy begets exclusivity and intentional power imbalance, and society as a whole needs less of both.