GM first investigated the unibody pickup idea in 2008, when rising fuel costs triggered a drop in full-size pickup sales. In theory, the smaller truck could allow the company to utilize global resources (Holden, at one point, was said to have contributed the platform) and help improve its CAFE ratings.
GM chose to abandon the idea after it found both price and fuel economy goals couldn't be reached. According to Automotive News, internal research showed consumers expected a less-expensive vehicle if it couldn't tow or haul as much as a conventional pickup. As for fuel economy? Tom Stephens, GM's vice chairman of global product development, noted, "as we dived deeper into it, there wasn't much additional fuel economy to be gained."
For now, it seems as if the Honda Ridgeline will remain the only unibody pickup in the North American market.
Source: Automotive News