Capitalism is a hierarchical accumulative system where all available means are used to accumulate capital and concentrate it. The state evolved alongside capitalism and the pioneers of capitalism voluntarily used state institutions like central banks and state-sponsored
Bankers were always integral to capitalism and consolidating their power via central banks or forming family networks like the Rothschild dynasty is a capitalistic mechanism. Before the “evil” Federal Reserve there were moguls like J P Morgan who essentially bailed out the U.S. banking system from the Panic of 1907 and thus made the notion of a central bank appealing. The U.S. federal government was a mere 5% of the GDP in the late 1800’s and a handful of ultrawealthy moguls voluntarily called the shots and owned elected officials. I am sure the factory workers and children working in mines in horrific conditions would have enjoyed a discussion of the voluntary aspects of capitalism or the “free market”, just as abused exploited workers in Bangladesh or Vietnam making cheap clothes or shoes you buy at The Gap or Old Navy would like to talk about “voluntary” aspects of corporations running their states and having global sovereignty over states.
Capitalism today is embedded via its natural evolution in corporations, efficient machines of capital extraction and accumulation from Asians and Latin Americans making Iphones, shoes, clothes, cheap stuff you buy. The voluntary aspect of transnational corporate capitalism is one-sided and hierarchical. The higher you are on the capitalism hierarchy the more voluntary options you have to make wealth. When you are a kid in Bangladesh making clothes in a factory liable to collapse, your participation is not very voluntary. if you are a cocoa slave in the Ivory Coast, you are being involuntarily used for the shareholders of a candy company, its management, and the person in the 1st world enjoying the chocolate made affordable by slave labor.