Well, I will have to blame my father for this. As long as I can remember, my father has been calculating his milage for each tank. I have continued this way as I am quite frugal, or cheap. I really do not know which.
The nature is also a good reason. I love fishing, sailing, hiking. I try not to spoil my environment.
In my opinion, it does not really matter what you think about the global warming theory. I feel that wasting energy and raw materials is basically stealing from ones own kids. However, everyone makes his and her own choices, and I cannot critizise anyone..
Btw. Here in Finland, half a year after taking your driving test, you have to take a second evaluating drive with your instructor. During this evaluation, fuel economy is also evalutated.