First, taste — nothing compares with the wonderful flavor of foods that are home canned or bottled! Commercially canned foods and bottled jams and jellies just do not taste the same.
A second issue to consider is cost. It used to be that it was always more economical to bottle your own food, even when it was purchased at a produce stand or farmers market. However, today is a different story. Unless you can grow your own produce, buying some to preserve will most often cost more than buying commercially canned foods.