Organized crime exists since the beginning of mankind and during its evolution, some ethnicities created their own groups and types of hierarchy, which I believe its created by natural way, meaning who was the strongest or most powerful or clever member. As someone already said its in the longetivity of the groups, especially the ones such as Cosa Nostra or the Triads. I also think that its the medias and the ordinary citizen fault for labeling all oc groups as "Mafia"