It’s all about numbers and defensive position. What he states about a historical perspective is true but using a much to short a period. All through history it has been the same. Ciity states, walled towns, castles, and early forts in the US all were developed out of the need for protection from hostile forces.
Early American settlers were targets of indian parties that could not survive without defensible positions. The same thing happens in modern wars with forward bases. It is not about where or how you live, it is about keeping people out and the ability to defend. If you have stuff other people want it will not matter where you are. If you want to keep your stuff you will need a controlled perimeter and the ability to defend the perimeter 24/7.