I'm actually going to fault regulations on this one. The EPA bases fuel economy requirements on the wheelbase of the vehicle. They used to publish a range of values based every other year or so, but then changed it to a formula. The formula is non-linear, making it neigh impossible to build anything with a small wheelbase anymore. In theory, they could design a small hybrid truck, but would need an obnoxiously long bed to compensate.
I watched a YouTube video on it not terribly long ago, and iirc, a 95 Ford Ranger, if held to the current formula-based regulations, would need 60+ mpg to be produced without major penalties to the company.
The EPA either needs to reevaluate the formula, or start manually publishing the numbers with values that are actually achievable by the industry at scale. Basically, by publishing the formula, manufacturers are able to min-max their designs in all the wrong ways.
EDIT: Updated for clarity and fixed some typos