I think this goes to a basic mindset in our population. One of convenience, disposability and entitlement. Plastic wasn't even in widespread use until the 1940's, and it certainly wasn't used for grocery bags. Plastic garbage bags weren't invented until the 1950's and were for commercial purposes. In the 1960's garbage bags for home use were introduced. Civilized people have lived clean and happy lived for centuries without using plastic bags to carry things, line their trash bins, clean their litter boxes etc...Many people currently manage to not use plastic bags and somehow remain sanitary and efficient.
--There is a grocery store chain in the state where I live that has never offered free bags of any kind. They have a grocery cart at the end of the checkout belt that all your groceries get placed in. Then you take the newly filled cart to the "wall counter" where there are boxes (that the groceries were shipped to the store in) you can use your own bags, or the recycled boxes. Incidently you can purchase heavy duty plastic bags from them, but most people don't. It is a grocery store that is frequented by very low income people, they just don't have the money for frivolity. I have NEVER forgotten to bring a bag to THAT store. And if I choose not to, I know there are boxes at the ready.
--Fabric can be washed, bleached &/or boiled. All those things will return a natural fiber cloth to a sanitary state. I have cloth diapers that I'm sure had poop and pee in them for most of their lives...smell fresh as a spring day when washed and I'm certain are not rife with bacteria. I have glass canning jars that have been used in the chicken coop, kicked around in the basement, covered in all manner of bacterial science experiments at one time or another...washed and boiled they are clean and safe to be used again. My stainless steel trash cans can be filled with greesy, grimey, gopher guts and then I can empty them and sterilize them to a state of fresh newness. On the flip-side, my mother's tupperware (as well as the inside of every plastic re-useable container) smells funny and kinda freaks me out!!
It requires a change of thought process and behavior to realize there is a different way of doing things and then take action to do it differently. If the stores didn't offer any bags, the question "Paper or plastic?" would cease to exist. People would learn quickly that they had to fend for themselves and they would take measures to do so.