Currently Online 
haxxiy on 09 January 2013
I think it has to do with the definition of marriage. It probably came to be from ancient religious rituals concerning the bonding of two or more people for the purpose of procreation. That would make sense within evolutionary psychology: lots of animals have partners for life so it seems reasonable an institution of some kind would come to exist around it.
Anyways most civilized countries equal civil union and even stable relationship to marriage on grounds of rights and obligations so nowadays it would be mostly a bragging rights award, honestly.
