Traditions, customs and prisoner's

I think that one of the advantages to following social norms as opposed to always doing the "rational" thing is that there are some problems where the ability of members of a group to rely on the coordinated behavior afforded by their customs and traditions can provide greater benefits to most if not all members of that group than if they each pursued their own rational self-interest.  Consider the Prisoner's Dilemma, for example when foisted upon members of a culture like the Sicilian Mafia.  If they all abide by their cultural values and keep their mouths shut, then they beat the game.  The use of cultural norms and peer pressure here is so effective and powerful that our government had to resort to extreme measures (like passing the vague and often over-reaching RICO laws, property seizure and property forfeiture laws, many of which poke their thumb in the eye of the U.S. Constitution.)