People buy trucks for two purposes: utility (ability to haul loads, etc) and transportation. The higher utility comes at a price (more gas), and in general this

People buy trucks for two purposes: utility (ability to haul loads, etc) and transportation. The higher utility comes at a price (more gas), and in general this balances with how frequently you require the the utility of a truck. Currently, gas prices are low, so someone who uses the utility less frequently may be more inclined to purchase a truck.