Imo the only world in which hydrogen becomes a viable energy currency is one where there's vast amounts of highly centralized power generation, e.g. fusion (but

Imo the only world in which hydrogen becomes a viable energy currency is one where there's vast amounts of highly centralized power generation, e.g. fusion (but possibly also off-planet generation) that needs to be effectively distributed to agents that can't be connected to the grid, like planes or to a lesser degree cars.