inter party fighting = more GM oppoutunities
Bad GMing? This is a role playing game and the characters are in a role. If the characters say are practical jokers and often take it out on their fellow members are the other not going to get upset after a while, and possibly retaliate? Two Chraters fight over a magical item, the rogue is contantly trying to PP the other member's pockets for it, or etc. These are only a few examples. but I belive the nature of a role playing game is just that a role play. If the characters do not favor one another then it is the GM's task to Master the Role playing, as a would he/she an encounter, an intricate dealing with an npc, an arch foe that constantly harasses the players.
Many things can be done by the GM to thwart the infighting while staying within the parameters of his own adventure -
Two characters are fighting, they fail to notice the approach of XXXXXXXXX where they are caught flat footed etc. / Thier poor demeanor causes neg modifier reactions to npc encounters, a key NPC may refuse to fight on their side or offer aid, while they are squabbling etc.
I feel it just gives the GM more to work with, yes it can be a pain at times taken too far, but it up to the players how they interact with each other and the world around them.
In Summary - It just gives the GM more opportunities to add glitz to the personal interplay of their game. If you don't like it in your game then, IN GAME teach the players why it is bad, but never force them via house rules.
Freedom, is only survival in this decaying wasteland we call life.
Peace, a lost realm of the forgotten.