Why is controlling violence without a state so difficult and costly? Do you think there are other possible ways to have a peaceful society without a state/government?

Bates discusses a fascinating example of "peace without a state" in his discussion of the Nuer (43-45). He argues that the Nuer constructed a society that provided some peace without the threat of state violence, but it came at a great cost?

Why is controlling violence without a state so difficult and costly? Do you think there are other possible ways to have a peaceful society without a state/government? 

metrials to use:

Bates, Violence and Prosperity, Snarr and Snarr, ch. 6, 8