The US, having cheap gasoline, uses gasoline vehicles in far more roles than say, the EU does, where diesel is far more common. "Light commercial" might as well read "should have been diesel" from an MPG standpoint.
By the way, diesel is now typically more expensive than gasoline in Europe too, and the tax embodied in the price is roughly proportional to the carbon content of both. In the past there used to be a lower tax on diesel in some countries as an aid to farmers and the transport industry, but it is less common now.
Really? Which countries? Not in the european countries I'm familiar with.