Plastic bags are a nightmare for the environment because they take so long to decompose. Lots of people use them as bin-liners for small bins so you are getting another use out of them, but they still stay in the ground as long.
Here’s a brilliant idea. It’s a bag that you buy from the shop with your groceries that, when you get it home, becomes a full size bin liner so it means that the small carrier bag and the large bin liner are one and the same thing. I wish I had thought of that.