The moral high ground

According to my interpretation of evolution (which I apply to just about everything under the sun, from organisms to organs, and from motion to emotion), there is, or was at some point in the past, a reason for everything that exists. Sometimes the thing continues to exist after its reason disappears (like certain architectural features that used to be necessary but are now merely ornaments) and some responses are exaggerated, but as a general rule, I find it useful to try to figure out why things exist.

Why, for example, is there such a thing as the feeling of "moral superiority"?

The other day, a colleague mentioned that he took the stairs and not the elevator not so much because it was healthy, but mostly because it was better for the environment. I bike to work when I can, always fill the dishwasher to capacity, and regulate the pressure of my morning shower so as not to waste hot water (less pressure means less water, but it can also be less hot, because less water splatters off). (I almost added that I only wash the car a few times a year to save the environment, but that would be less than completely truthful: mostly, I just hate washing the car).

I have been doing these things so long that I no longer really have any feelings about them, but when I first started "saving the environment", in my late teens, I distinctly remember feeling morally superior over those around me who did not. Of course, I did my best to hide this from other people - nobody likes a snooty, smug, self-satisfied do-gooder, but now, many years later, I wonder whether I would have ever done them had I not had that feeling as a reward.

Can it be that we as a society actually need snootiness, smugness, and feeling of being moral superior to help us do things that are better for us in the long term? And if so, should they be reclassified as virtues? If so, is my disdain and dislike for snooty, smug, morally superior self-satisfied people also a virtue? :-}