Could the thinking go back to the WW2 and North Africa where they found the 2WD drive trucks outperformed the 4WD and went back to 2WD for the long range missions? I think there was more to it than the drive, the 2WD were Chevrolet and the 4WD fords, the Chevys broke down less as they were simpler, also the 4WD used a lot more fuel. They found then that big soft tyres were more use on sand than 4WD.but that's a very specific set of circumstances. Still maybe the lesson got over applied? After all this is only some 15 years later.