I'm arguing against the use of friendship to win more games, not friendship per se. You can make friends without building trusting each other in the game. Just play with the understanding that you are ultimately competing. If I'm playing a game of monopoly with friends, it's understood we're playing to win. If two players decided to pool their resources, they would do quite well, but this would not be accepted.
There is potential for confusion here. A person who betrays at will is more likely to win that game. But a person who doesn't betray his teammates may win more games overall, as he can trust that person to not betray them next game. But this is more boring, players should be focused on winning the current game.
