Because the ability to use force is generally a monopoly of the government, precisely for that reason.<p>A better question would be &quot;how can I be sure that capitalists and government won&#x27;t cooperate for establishing monopolies&quot;? For that, I don&#x27;t have an adequate answer. At least, in capitalism, there are competitors lobbying against it, creating some virtual political market. Full government monopoly is generally much worse.