[oil]

- pointing out that you think an agreement is unlikely to last because one party will probably be tempted to break it doesn't actually justify someone breaking it.

- pointing out that this is a game and/or that everyone only does something if they stand to win something because of it, is also a pretty shit justification for going back on your word.
If you turn up for a game of football in the park with some friends and you reach an agreement not to shoot inside a certain range, then go ahead and start breaking that agreement because you start falling behind, you will look like a dickhead and no one will like you. For good reason.