Water + Electricity = Hydrogen. Pretty simple. But it's just not worth doing on a major scale at the moment.

Oil and gas are so favored because they are "free" energy. They require some energy to extract, but the energy density is high and a surplus results. Now, you could mass produce hydrogen, but why do that when you can just use electricity? The fewer times you need to convert energies, the less waste you'll lose to inefficiencies. Affordable electric cars suitable for general commuting are perhaps only one vehicle generation off.

One possible counterpoint is that certain machines may need the energy density of a liquid fuel to perform optimally. Electric cars and lawnmowers are not known for their rugged power. I could see an industrial use for hydrogen as diesel obsoletes, though it would carry a premium price.