Yeah, FWIW, this kind of bag fee is very common in the U.S. as well, with the same effects (though perhaps not in northern Michigan). In fact, single use plastic bags are outright banned in many parts of the U.S. I guess I'm not sure what GP means by "No one ever talks about paper bags."
I guess they mean that paper bags are biodegradable and have been for ever. However, plastic bags have been used instead as they are cheaper. He says cost is what drives this so for a barley or corn plastic bag to work it has to be as cheap as a regular plastic bag or at least cheaper than a paper bag.