I think we have a primitive instinct based in survival programming that prompts us to grab just a bit more than we need whenever we get a chance. Mindless territorial game-playing eventually leads to having more enemies than friends and in today's changing environment, if you want to be in the loop, you need friends. You don't want to be a patsy.
Scientific research shows that unquestioning cooperation invites exploitation.
So those people set themselves up to be victims. A manager with a low self image will tend to feel insecure more often. Those insecurities wake up the survival programming that drives territorial behavior. That manager is more likely to mindlessly withhold information, engage in discrediting gossip, or take up brown-nosing. On some level, playing territorial games is a way to protect what we value.