It’s not that it’s a bad fuel source but it seems to be very hyped and currently not very economical nor is it as safe as other fuels (highly flammable etc). In order to accommodate it, other prototype aircraft have had to remove space for passengers because of the size of the fuel cell required, for instance.

I would be the first to say that I am open to persuasion and am by no means as well educated on it as I could be so always happy to be directed to reliable sources of info.