Why could we not protect ourselves? Many ancaps or ancoms would argue that would be possible. The government assumes they know better than you do on how to enforce contracts or protect yourself and impose a monopoly on force by force to make sure you can't build alternatives. So yeah, it is based on the premise that they know better than you do on certain areas of life. People just disagree how wide these areas should be. I may be mistaken though so feel free to prove me wrong.