Every serious study of post-catastrophe survival has found that cooperation with others, rather than individual isolation, is the optimum strategy. The prepper culture, though, is fanatically individualistic. If the government did offer a comprehensive civil defense program; with stocked, assigned shelter space (as in Switzerland); the RWNJ preppers would reject it as some kind of collectivist conspiracy.
Each doofus thinks he and his family unit can survive indefinitely on their own. This would be viable if they were alone in the world, like Swiss Family Robinson, but that is not the case here. No group of 4 or 5 people is going to have the necessary cross section of skills.