Obama on car maintenance

Are people really making a fuss about Obama's urging people to properly tune their engines and inflate their tires in order to save gasoline?  No one I read is, but perhaps I read only exceptionally sensible bloggers.  The thing does sound slightly unpresidential--no one wants the Commander in Chief nannying them about their lawn maintenance or checking to see that the carbon monoxide detectors are properly installed.  But it's hardly worth mentioning, much less mounting any sort of actual criticism.

One thing does puzzle me, however:  why do so many people drive with improperly inflated tires?  Forgive my ignorance, but having grown up in Manhattan, the world of car ownership is as a closed book to me--I just bought my first real car in my mid-thirties.  So what's the deal?  Does it make the ride more comfortable, or are people just to lazy to put a little air in from time to time?