Grocery bags are disposable plastic. In my state they cost a few cents each as of a couple of years ago. Reusable bags are common, but it's also common to forget them and need to buy disposable bags. Most people reuse them as e.g. trash bags for bathrooms.
They dropped plastic bags where I'm from. 25c per paper bag. $2.50 for a bag for cold stuff. It does add up, then what do you do with that stuff, they can't be bin liners