The real problem is with the game design, not the players.
Any of you guys watch pro games? starcraft, warcraft 3? There are some amazing comebacks out there. A game shouldn't be over till it's over. The fact that a game can be "over" in Sins, and yet still drag on for another hour.. that's just bad design.
and there lies the source of the problem, if you allow players an oppourtunity to exercise lame play then sooner or later a suprisingly large number will and then the game allows them to slip anonymously off to do it again...
Its all too common in MP games.