Yeah, every time I'm in the states (well, Florida) I've noticed that. They should add a charge so they won't use them at all. I know some places already do.
We have to bag your stuff unless you ask not to. If wal-mart charged for plastic bags, I'm pretty sure a lot of people would actually bring their own bags or don't use any.
I don't really mind. Like who wastes plastic bags? I guess gross people without those tiny trash cans. Seriously the best part about shopping is getting free trash bags for the little trash can