[f1refly]

I've been packaging cat food when I was in high school and they do that because, when a single of those cat food packets rips open for whatever reason, the smell is pervasive and intensive. It spreads through the whole warehouse, from a single open bag, getting ever worse as it spoils. The plastic lining in the displays is to protect the shipment - think of an the oilsump the cellar which contains a houses oil tank is lined with. It's a way to contain the spread of a hazardous substance in case the probably containment unit fails.