The amount of plastic we use is sad. When I go to the grocery store, the apples are wrapped in plastic, broccoli wrapped in plastic, baked goods are in plastic, plastic everything. Why do they do this? I'm going to wash the produce when I get home, I don't need a plastic wrapper on my broccoli just to throw it out immediately and then was the vegetable anyway.
Plastics are made in huge quantities from by products of oil, gas, and coal.
Petroleum is decomposed under heat into gasoline, kerosene, naphtha, light oil, heavy oil, etc. Most plastics use naphtha as main raw material. Naphtha is further decomposed thermally and separated utilizing the difference in the boiling point (temperature at which the phase change from liquid to gas occurs) to form ethylene and propylene, which are the raw materials for plastics.
Chances are the electricity that you're using to read this was generated by oil / gas / coal; the world runs on oil.
Plastics are essentially a convenient by-product, which can be made cheaply and in bulk, and they do a good job preserving foods.