Some of us just think that we, as a society, can do better than enforcing our beliefs and demands at the end of a gun barrel. And we prioritize principle over outcome, acknowledging that every system has it's pathological edge cases - including the current system.
The big problem though is that the pathological edge cases of our current system are much better than the extremely pathological normal cases of a system without checks on what people are allowed to do.
I mean, anarcho-capitalism is basically what sovereign nations are at a smaller scale: Factions of humans who make decisions without any real checks on their behavior beyond the environment and the reactions of other factions. And I'm supposed to want a microcosm of global politics in my back yard? No thanks, taxes are fine, please fix the roads so I can get to Chipotle.
The only reason I could see for anyone wanting anything approaching individual sovereignty is if a) they somehow believe that there is no bigger fish in the pond, or b) they're really so naive to have no idea what other people could be capable of doing to them.
