No. There is no readily available supply of net-positive-energy hydrogen on Earth, where most human power usage takes place. Hydrogen fuel cells may be a useful component of a total energy system but they are not a source of generation capacity. Hydrogen is more like a battery than a supply of energy. Hydrogen can be liberated from water by using energy. ...
Under RDE [Real Driving Emissions test], a car is driven on public roads and over a wide range of different conditions..... Conditions include:
Low and high altitudes
Additional vehicle payload
Up- and down-hill driving
Urban roads (low speed)
Rural roads (medium speed)
Motorways (high speed)
There is another possible reason, just a theory mind. Small cars may pass emissions testing without the need for the technology whereas large cars must have it to pass. In other words, it is not necessary for small cars to have the technology to meet emission requirements.
(although of course, the vehicles could, with start-stop, still benefit from a 12% ...
The focus on electricity is probably secondary: Any energy source can be converted into electric energy.
The focus on fuel cells is probably secondary, too: Hydrogen can simply drive combustion engines as well; if the hydrogen and oxygen sources are sustainable, then the combustion engine will be as sustainable as the fuel cell (minus potential efficiency ...