Self-sufficient bunkers are a whole different level of dedication to worst case scenarios (and of course unlike the soap shelf for potential barter it doesn't really work if you're a city dweller). Also it's a lot more work. I mean, with food stuffs you have to replace things all the time, and then how long do you plan that to last? Because if things reach the zombie apocalypse level of breakdown where things deteriorate so much that you can only make it with guns and bunkers, what is the point really?