Megan McArdle (not pictured above) asks:
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?
A couple commenters hit the nail on the head. Basically, maintaining proper tire pressure is a giant hassle (note the distress evident on the face of the woman in the above picture). It's more trouble than it's worth. The pressure gauge that never seems to deliver a consistent reading, the hard-to-access valves on the tires, having to squat, kneel, or sit on dirty asphalt, dealing with the hose getting stuck under a tire, the noise of the air compressor, the car behind you impatiently waiting to use the air (who you invariably assume is an expert at filling tires and looks down on you for taking so long), etc. etc. ad infinitum. All for 2-3%?!? It's probably worth it over the course of a year or so, but that's tough to convince yourself of when it actually comes time to check the pressure.
If someone came up with a product or system that dramatically improved the tire pressure maintenance experience (and was cost effective), I bet they'd be successful. Imagine if all the whole process was automated, so that all you had to do was park your car in special stall and little robotic arms would locate each of your tire valves, unscrew them, check the pressure, and add or remove air, all while you sit in the comfort of your vehicle. This sounds like something they'd have in Japan...
Image from Flickr user squashpicker available under a Creative Commons license.