The principles behind anarchism are great, but the challenge is that what would happen if there's no control at all from a legal entity (like a government) to put restrictions and limits to the people?
Certainly, if there wouldn't be a government, you and me would probably be dead by now. There has to be some kind of control or legislation that puts limitations in order to avoid people doing unethical things like murder, theft, destruction, corruption, etc.
Like you said, people can voluntarily pay for their security, but how secure would you actually be? So far in history, nobody has come up with a form of government that includes anarchism with guaranteed protection, safety, and well being for all citizens of a nation.
Do you believe that form of anarchism will occur at some point?