My definition of self-sufficiency is to be able to live your day-to-day life without being dependant on anyone else. By that definition, no one will ever truly be self-sufficient, but I still think it's a goal worth reaching for. There are people in our own country that are close. I keep getting closer every day. I already know me and my family will never be completely self-sufficient. Then why bother trying?
To cut down on dependancy of oil. Let's face it, oil is running low. Think about how much oil is involved for you to go to the grocery store and pick up a bunch of carrots. The carrots are grown in a field which is plowed with a tractor that uses gas. Then the carrots are harvested with another gas-using tractor. And the person who is driving the tractor probably doesn't live on the farm where he works. (S)he probably had to drive to work in a car or truck. Then, once the carrots are harvested, they are loaded onto a truck which, of coarse, runs on diesil, and the truck transports the carrots to the grocery store. So then you get in your car and drive to the grocery store and back to get your carrots. Now let's say you grow carrots in your own yard. You walk ten or twenty feet from your door, prepare the soil by hand, plant the carrots by hand, pull them by hand, and eventually walk back into your house to eat the carrots. No oil involved.
To know where my food is coming from. I've always been on the picky side when it comes to food. It plain grosses me out to not know where my food is coming from. Every few months there is a brand new news report out telling us not to eat this or that because it's tainted with one poison or another. I don't use anything on my food that is not organic- and especially no pesticides. So I know exactly where my food is coming from, down to the square inch of soil where I planted the seed, all the way through the growth cycle and onto my family's table.
Because it saves money. For less than half the cost of the bag of carrots I could buy at the store, I could buy a packet of seeds of carrots and have carrots for the entire year. Depending on the variety of vegitable, I collect the seeds and carry them through from one year to the next. So let's say instead of buying a bag of peas at the grocery store for $2, I can buy a packet of pea seeds for $1. Then when the growing season is over, I can collect my pea seeds every year and have peas indefinately.
Because it's fun. I enjoy the challenge of thinking up new items around the house I can make myself and depend even less on other people to provide for me. Self-sufficiency does not just have to do with food, but every facet of life. I make my own laundry soap and body soap, for example. These are really fun to make, so it's a hobby as well as a lifestyle choice.
Those are the main reasons, not in any order, that I choose to be self-sufficient.