During my peak driving life (from age 16-30 or so) the price of gas was basically not much more than a dollar per gallon for most of the time. Even in my relatively poor years, except for very long trips it was never a high enough price that I'd factor it in when considering to make a car trip. Sure I might grumble when it was time to fill the tank, but I never thought in terms of "how much will it cost me to make this trip."
At $4.50 per gallon in many places I guess that changes. If you're getting 20 mpg, a 50 mile round trip commute will cost you $11.25. The 13.2 mile trip from downtown Minneapolis to the airport, which you can do on the train for $1.50, costs 3 bucks by car.
The point I'm trying to make is that when gas was cheap, people thought in terms of the cost of filling the tank rather than the cost of making a trip. People didn't really make a marginal cost/benefit calculation because they didn't really perceive the cost for short trips. That's changing.
