I agree. And I don't like governments either. But I think it is a question of balance of power. As long as competition is actually free, this can happen. But there is a shift when one actor get enough power to kill the competition. I think governments/states have played a role in maintaining competition in some areas with antitrust laws, and have also killed it in other areas.
I just don't see how private justice could be as effective at balancing power and limit its concentration in an anarcho-capitalist world.