They aren't necessary. That's not the point of any of this.
The only point being made, as explicitly pointed out in the explanation you failed to read, is that policing institutions are not inherent or necessary to community enforcement of norms and laws, contrary to the copaganda pushed in the modern day. This is, and I quote my fucking self in this very comment section, "An unusual point of unity between an ancient polity noted for its sense of hierarchy, and hierarchy-averse modern anarchist ideology!