The problem with the ancap is between one or both of the following:
1) impossibly high eternal vigilance: without police, courts, etc to enforce property rights… you end up merely possessing them by strength at arms. Technically speaking, that is the ONLY way to ever have it (you own nothing if criminals can take it at will), but a functional government allows you to do things like vacation away from home or work 10-15 hour days away without having to worry about whether you have enough traps/guards/etc defending your place.
2) competition in force: me and my close friends are troupe A. We defend our properties on a rotating basis since there are no police or courts. Another troupe—troupe B—has a dispute about a property line between one member of my troupe and one of mine. Troupe B is being unreasonable about it. Both troupes have a NATO article 5 defense pact. The obvious end result is the same as point 1–the boundary is decided by elimination of the opposing group.
Government, when it is properly subordinated to principle, is the best defender of property rights.
The issue isn’t government as such, but the fact that they have not been properly subordinated to principle since the early 1900s.
Sadly, the mass importation of European immigrants around that time that did not keep or bear arms and could only vote for whatever expanded industry’s pull in government is part of this. I say it as the descendant of that wave.