Another huge expensive problem is transporting it is not easy. At room at atmospheric pressure and temperature, it takes up like 2-3 grams per gallon of space, making it super inefficient to transport.

You could pressurize it, but that makes it insanely flammable and a risk of it leaks. You could also cryo-freeze it, but that is also very expensive to transport, it require a lot of energy to freeze it, maintain it during long transports, and to unfreeze it at it's destination.

Building a hydrogen delivery infrastructure is probably the best way to overcome this, but that would also take years and billions.

I'm no expert on the field, but I'd imagine a lot of energy departments would rather do that cost and effort towards building new green energy plants that can deliver power to grids rather than only help cars. Car-wise, most things are transitioning to hybrid or electric anyways, so they also benefit from a green power plant.