Unless you have supercruise capability (which only four fighters in the world have) flying supersonic consumes and enormous amount of fuel, so flying any distance at supersonic speeds pretty much requires aerial refueling. IIRC you also need special permission to fly supersonic in US airspace. If you're limited to subsonic speeds then there's really no advantage provided by a fighter. Private jets can fly at similar high subsonic speeds (0.9-0.95 mach or so) and are usually cheaper and more efficient to operate than fighter jets.