By and large, people do what is comfortable. They have a lot of things to worry about and they are just trying to get by. If something becomes easier, cheaper, or more convenient, they may well change their behaviour (although sometimes even then they won’t). But by and large they are unlikely to do so out of the goodness of their hearts – not in the big numbers you need them to. When Britain was facing down the Nazis across the English channel, we didn’t rely on wheedling appeals (“if everyone just ate one egg per week, we could build a hundred bombers!”). We rationed things and imprisoned those who smuggled them.