Who is "so many people"? From my view, 95% of the people I know (in a very liberal area, btw) don't consider their carbon footprint at all. They don't want to give up cheeseburgers, fancy cars (aka 2 ton wheelchairs), or living in their specific way. The idea that I want to bike to work, for health and emissions, is met with: "Wow, you're taking your life into your hands whenever you don't drive a car".