Can you even imagine people paying a tax on plastic bags? Just eliminate them. This way it's less of a hassle for everyone, and we are helping the environment. Additionally, then we wouldn't have to keep plastic bags on hand in case we get that one random guy who will pay the tax on them.
Taxing the use of plastic bags could raise revenue. If people don't want to pay the tax, they will take their own bags to shops, or shops will have to assume the cost thus look for better alternatives. Why ban them when you can profit from them and help the environment at the same time?
Due to the convenience of reusable bags, I believe that cities should not outlaw plastic bags. For example, many people reuse plastic bags to hold used oil and clean up after their pets. As a result, people have a practical way to dispose of refuse and there is less litter on the ground.