I don't get it, what's this bag good for? It's just a bag.
In most parts of the world (at least in Europe, Asia, and recently in California), grocery bags aren't free.
Paper obviously comes from trees, cutting down forests, and cost money to plant more trees. Most plastics are made from Petrochemical, a depleting resource, and has thus resulted in Government Regulations. Stores have started charging for them. I've even heard of some bans, due to problems with landfills.
It won't be too much longer before "Paper or Plastic" is a thing of the past. It is becoming more common (and expected) to just bring your own bag.
Well, I live in Sweden, and we usually buy paper bags that we later use to store junk for recycling. Sometimes I buy plastic bags when I don't want to carry around paper bags, since they're more cumbersome to carry around. But I usually use those as trash bags afterwards.
Maybe Doopliss isn't kicking ass, but he's taking names!