If I remember correctly, there was a study done years ago on reusable bags that found them to be breeding grounds for harmful bacteria. How many times do you purchase meat in packages that leak blood? Add to that the occasional leaking milk carton and whatever else is available and the bags turn into a Petrie dish of bacteria just waiting for your next purchase.
The solution is to find a use for old bags. Then people will be more inclined to properly dispose of them. In communities where I have lived, grocery stores promoted and provided for bag collection.
Well, we have one running for President right now. Two, if Senator Sanders decides to pull a Bruce Jenner.