Reusable bags made out of fabric have been linked to the speading of bacteria on food which has been known to make people sick. And if people wash such bags then they have to take into account the carbon footprint of both the washing machine and possible use of hot water. Possible envirnomental unfriendly washing detergent going down the drain must also be considered. And then some people probably use a dryer to dry them.
So the green movement needs to do its homework before alarming people.
The irony is that with trees in abundance and oil so expensive that it makes plastic less economical, biodegradable paper bags are probably going to end up being cheaper anyway. LOL.
It's probably best to not be 100% pure on the issue. Use the cloth bags for well packaged things like cans or boxes and use single use bags for leaky, potentially messy items like meat, produce and milk (one leaky bottle can mess up the outsides of dozens of others in the case).