I've us the same e peanut butter jar several times by refilling it with freshground peanut butter at a local natural foods store. Glass jars are also great for storing all kinds of things, like nails in the workshop or dried herbs in the kitchen. If that isn't enough to scare you, consider that packaging accounts for one third of all landfill space. More than half that packaging is plastic. Plastics are used for an ever in increasing variety of disposable as well as durable goods.
Plastics are inexpensive to produce are versatile.
But tremendous energy inputs go into making plastics, and they break down slowly. You'll also get between two and five cents back per bag at most stores. You might also try reusing plastic bread bags to buy bulk foods the next time you shop. Avoid disposable cameras. Again, the price of convenience is high.