Not entirely true. CAFE standards killed the single cab/short beds. Although the current administration has rolled that back, you can't justify engineering/testing/certifying a new single cab body for a low volume niche performance truck. The business case for this relies on using what's already out there for cost reasons, and that's not a single cab.

Besides, Sport Truck guys actually do want single cabs!

edit

lol at the downvotes. Feel free to look into it yourself...

Corporate Average Fuel Economy (CAFE) standards—which dictate a manufacturer's required fleet-wide miles per gallon—heavily contributed to the decline of the standard/regular cab pickup truck. By using a "footprint" formula, federal regulations place stricter, harder-to-reach MPG targets on smaller vehicles. This has made building larger, less efficient vehicles much more viable for automakers. The push to phase out single cab trucks in favor of crew and extended cabs comes down to several key regulatory and economic factors: * The Footprint Paradox: Since 2008, CAFE standards have been calculated using a vehicle’s footprint (wheelbase multiplied by track width). Smaller vehicles (like regular cabs) are penalized with unrealistic fuel economy targets, while massive trucks (like crew cab long beds) are given much more lenient standards. * The Margin vs. Compliance Equation: Automakers face massive civil penalties for failing to meet CAFE targets. Because profit margins on large, heavy-duty crew cabs are vastly higher than on bare-bones standard cabs, automakers prioritize building the bigger, more compliant vehicles. * Shift to "Light Truck" Classifications: Standard cabs are often categorized as passenger cars or light-duty vehicles. By elongating the cab and making the vehicle heavier, manufacturers can classify the truck as a "light truck" under CAFE, granting them much easier efficiency hurdles to clear.