We'd go in the morning to the post office, then later for banking, and after school for groceries for dinner. In 1974, we as a society rethought that routine. We started doing our errands in one trip. We started driving slower and eliminated unnecessary trips. The concept of supply and demand works here.
Prices stay low if demand is low.
Of course, using less gas also saves money. A small import vehicle saves gas. If you drive a full size vehicle, you pay dearly at the gas station, and waste valuable resources. The convenience of a larger vehicle is not offset at the gas station. Gas is not the only place to save money.