[Reason077]

Natural gas is fairly safe (non-explosive) while compressed. It has to decompress and reach a pretty specific ratio of air-methane mix before it becomes explosive.

Hydrogen, by comparison, is explosive across a much wider range of pressures and concentrations.

Hydrogen also needs to be stored at far higher pressures than natural gas in order to reach comparable energy density, which makes it more difficult and expensive to handle and transport.

[ncmncm]

We will not be using compressed hydrogen, so that doesn't matter. LH2 is kept at atmospheric pressure.

[Reason077]

Liquid hydrogen is also pretty difficult and costly to store and transport, because it requires cryogenic storage. You need to make sure to keep it at −252.87 deg C or it's not going to stay liquid for long! It also takes a lot of energy to compress into a liquid in the first place, making it much less efficient as an energy carrier.

Hydrogen used to get used a lot by the space industry (Space Shuttle, etc), but now days the modern rocket industry has been moving to other fuels (kerosene, methane) - largely because of the greatly reduced costs of handling those fuels!

[ncmncm]

We are already quite well practiced in handling and transporting liquified methane, which in only incrementally easier than LH2.

Rockets are lately designed for methane in large part so that concentrating Martian atmosphere for fuel will be more practical, but also for CO2's greater molecular mass, important in an earthly first stage launcher, which needs absolute thrust, to get moving in 1G, much more than efficiency.

As fuel, LH2 may find use mainly or even exclusively for aircraft, but it is exceedingly valuable as feedstock for other work, including ammonia and, yes, methane synthesis. Methane is itself feedstock for many other processes. Ideally these would not result in released CO2...