Most trucks are work trucks. Crew cabs means more workers per truck. That's why one can typically find a lot more white crew cabs than anything else (at least in MD and VA). Also, its the end of the year. Many small businesses try to reduce their tax load by spending on deductible assets.
"Certain vehicles (with a gross vehicle weight rating above 6,000 lbs but no more than 14,000 lbs) qualify for expensing up to $25,000 if the vehicle is financed and placed in service prior to December 31 and meet other conditions."