A minarchist would argue that maintaining a monopoly on the initiation of force within a territory is the one legitimate function of government. An an-cap would argue for what is effetively a decentralized version of the same thing. The peer-to-peer legal system itself would act to behaviours not consistent with the NAP.
Discussion
The minarchist position has historically worked quite well (eg. Gilded age of America, height of the British Empire).
I have yet to see a successful ancap civilization emerge.
I have my own doubts as well, I generally agree with you, but what you call “civilization” may actually be a human settlement out of scale and unhealthy to the human animal. Where ancap settlements would have the freedom to disband and fracture into smaller ones. We may never see them because they don’t scale to a large measurable event. This does fundamentally mean the people in them are more vulnerable to outside aggression and servitude. I’m just also not convinced the scale of human settlements are right a
Nd it might be a trap to define success as one which reaches that size.