The fact that all citizens are afraid of state violence does not mean we can redefine word "voluntarism". You abide the law non-voluntarily. You abide terms of service in McDonalds voluntarily because you can always choose from millions of alternatives + you can have a peaceful dialog in case of a dispute. Neither McDonalds manager, nor you are willing to fight each other on fists or in court. It's in your mutual interests to figure out problems through discussion.

You don't discuss with the state. You can have your input, but you are totally dependent on existing powers that allow you some freedom and some voice. That's why you have no problem arguing with private companies and having them listen to you, but everyone avoids state courts as much as possible (in majority of cases courts are used as a threat, not as a real dispute resolution mechanism).