I don't think the cost of fuel is negligible in calculations like these even in the United States. At 3 USD/gallon, a ten- to fifteen-mile drive can cost enough to matter, especially if your car's gas mileage isn't great. Even the best-case likely scenario, a ten mile drive in a car that gets forty miles to the gallon, the gas price ends up being 0.75 USD, or an additional 16% cost. Worst-case examples could actually have somewhere between a quarter to a half of the true cost difference in fuel.

That's not as extreme as in other countries, where a twenty-minute drive could meet or exceed the time cost, true, but in many cases the distinction is rather extraneous. They're probably avoiding the fuel cost because it's far more complex to meaningfully calculate.