The differences are skin deep. Private corporations are just as capable of using force as governments are, and are often eager to "become" governments as soon as the opportunity arises.

Consider rent. The payments you make seem voluntarily when you have options, but living somewhere is indispensable. A landlord who acquires enough rival apartments can grow so large as to become a king, and at some point people stop saying "voluntary rental payments" and start saying "compulsory tax payments." But they are the same thing. A country is an apartment writ large.