I do not agree that supermarkets do what customers want. They do whatever will induce the customer to purchase the majority of their food at the supermarket. Plastic is not necessarily what people want if they are given a choice, but very often, as has been said, customers in a supermarket do not have a choice, so we cannot say that the supermarket is doing what the customer wants. Clearly, if customers do not have a choice, they take what the supermarket offers them. For instance, when I go into a supermarket to buy some of my fruit and vegetables, I normally do not have a choice as to what bag to put them into. I do not put loose tomatoes into a supermarket shopping trolley; if I had a paper bag to put them in, I would put them into that, but if there is only a plastic bag, perforce I have to put them into that.