The idea of voluntary simplicity is NOT that you HAVE to be self sufficient. It is rather that you need to consciously think about your spending (and consumption) habits and rather spend money on sustainable products (instead of disposable).

Self sufficiency is an added bonus :)

Of course you don't have to go the voluntary simplicity route to become a more responsible consumer. Many people already do this as a moral choice. Also, VS does not mean you will spend less money on a product. In some cases you will actually spend MORE to purchase a more durable product from sustainable sources.