The idea that a functional society can arise from a population that only does what it wants is, let’s say, unlikely. It removes checks and balances, so there is not really anything that prevents someone with huge resources to become a tyrant. What happens if someone with billions of dollars ignores the NAP to get their way? They can fund a private army, I can’t, so how can I prevent them from aggressing against me? Without a state law enforcement and legal system, there is no entity that can stop them. We would regress to a society of warlords, dukes and serfs.

Likewise it makes the country as a whole more vulnerable to enemies. If there is no central state to run the military, just a rag tag collection of powerful, self-interested groups, then could they successfully repel an invasion? What if they are bribed with power by the oppressors, and facilitate the invasion? Look at colonisation in Africa and the Americas to see examples of how that played out. Tribes played off against each other for the benefit of the highly coordinated invaders.

Libertarianism is a user-pays society, where if you can’t pay and can’t generate income (even if it’s no fault of your own) then you better hope someone takes pity on you and you receive charity, or else your remaining option is to just die. Our current system is a playground for the rich and a crushing, lifelong burden for the rest as we compete for relative scraps, Libertarianism would dial that up to 11.

Note that I live in a country where although government has its problems, there is quite a bit of pro-worker and pro-citizen law on the books, and government institutions are generally seen as competent and are trusted. If that wasn’t the case then perhaps Libertarianism would seem more appealing.