Why would they want to start a war in their own country? US start wars very far from its own borders. It's highly profitable and only small number of lives of U

Why would they want to start a war in their own country? US start wars very far from its own borders. It's highly profitable and only small number of lives of US citizens are in danger. But for US situation with NK and SK is already good enough: no profit from invading NK, and US already profit from having military base in SK because SK pays them huge money for it. USA gains nothing from invading NK. When any variable change and invasion will become profitable, NK will be inevitably "liberated".