The biggest advantage of hydrogen is that it produces no carbon emissions. Are there any other advantages?
Green electricity is made by windmills and solar panels. However, you can only store these electrons in batteries to a limited extent and they are also difficult to transport. Molecule storage is much easier and cheaper and the energy content will stay the same throughout time. It is also possible to refuel much more quickly.
Hydrogen is the most basic molecule you can make with green energy, making it the most energy efficient conversion, and the first step for any other alternative like ammonia or even methanol.