My biggest issue with them is how often it'll turn into some kind of environmentalism based excuse. They 'have' to clean the plate because they care ever so much about the environment and the preciousness of food. The same people who insist on driving rather than walking short distances, who get almost every single thing they shove into their mouth all day through factory packaging and distribution and who fund some pretty horrible practices because they don't give a shit where their low quality ingredients come from. They start giving lectures about environmentalism.