The institution of honor has a practical function as well as a moral one.  It provides a method of social control whereby tribes are able to police themselves.  While there is much more to the institution than this, this function alone makes it a critical one for maintaining order without external or imposed systems of law and punishment.

Reference: http://www.hf-fak.uib.no/smi/paj/LaBianca.html

 

Edited 1/26/06 tlc