Terrestrially you are correct, but space is a very different situation. There you can get plenty of energy, but volatiles are rare. H is needed for water (for

Terrestrially you are correct, but space is a very different situation. There you can get plenty of energy, but volatiles are rare. H is needed for water (for people) and propellant (for rockets). The rockets in particular are open systems and must be, so need a plentiful supply. If you can find a good source of Xenon, you can use that in some applications instead, but that's probably harder than H since it doesnt form more stable materials like H2O.