They won’t, because EVs will always be the better option, and the niche applications where an EV simply isn’t viable will be served by biofuels rather than hydrogen. It’s a mongrel of a product to manufacture, store, transport, and transfer into the vehicle, whereas liquid fuels can be stored in a fuel can, and transported by every means of transport known to man.
Hydrogen has been the fuel of the future for the last fifty years, and it’s still not a viable option.