Without violence, it's significantly harder to defeat griefing, nonviolent but antisocial behavior. The work required to overcome griefing significantly outweighs the work the griefer puts in. An example would be obstructing someone's path so they don't have freedom of movement or "theft" of assets in the commons that the victim was trying to earn, such as dealing the killing blow for XP after another player did most of the work.

I'm using "state sponsoroed violence" in broad strokes. Without PvP in player-governed game worlds, you can't even really enforce simple jail time.