Dependance begets subservience and venality, suffocates the germ of virtue, and prepares fit tools for the designs of ambition.–Thomas Jefferson, Notes on the State of Virginia
Society is composed of individuals and is a reflection of those individuals. It comes into existence because it efficiently meets the needs of members of that society. It cannot be created Ex nihilo.
In order for a society to come into existence there must be individuals involved in productive labor; labor which when combined with the productive labor of others allows those individuals to achieve a higher quality of life than was possible in isolation.
A self-sufficient person is valuable to those around them. Several self-sufficient neighbors exchanging the products of their labor can quickly eliminate their dependence on inefficient fragile systems which they previously relied on.
Though there are many items that typical individuals cannot produce, many of these items contribute very little to overall happiness. TV is wonderful and some of it can be very enriching; however, if you have a functioning TV does a new one increase your happiness for any significant period of time? Think back to before your last purchase of this type. Are you any happier now than you were then? If so, is that happiness the result of that purchase?
Unless one is willing to completely abandon modern society, becoming entirely self sufficient is probably impossible. (I’m certainly not willing to make that sacrifice.) That being said, self-sufficiency in particular areas is entirely possible without any major sacrifice. Growing vegetables, raising chickens, making minor repairs, etc, etc.
The benefits of self-sufficiency to the individual and the community are too many to list, but I believe the most import benefits are personal resiliency and increased value to ones local community. Self-sufficiency is the first step towards local autonomy.