Because the economics of storing and transporting hydrogen are just not great. You need a lot of energy and infrastructure to do it. And while the density per k

Because the economics of storing and transporting hydrogen are just not great. You need a lot of energy and infrastructure to do it. And while the density per kg is great. The density by volume is absolutely terrible because hydrogen is the smallest and lightest molecule. In liquid and gas form it's nearly 3x the volume of methane (for the same amount of energy). If you are transporting it in compressed gas form (like is common to supply hydrogen vehicles), it's about 18x the volume of diesel. Needless to say, this doesn't scale for things like supplying fuel stations. In liquid form, it's better but we're still talking 3x that of methane and 4-5x that of diesel. And to keep hydrogen liquid, you typically boil some of it off continuously: it doesn't keep for very long. Methane has the same problem except the temperatures and pressures are such that it's not an enormous amount. Liquid hydrogen has to be chilled to a few degrees Kelvin. If you ship it around, you'll lose some non trivial amounts over the whole journey. Most hydrogen produced today is used onsite to produce something else for this reason. Moving it around just adds cost and complexity. Terraform seems to have made some progress with hydrolizers. But before people start popping champagne bottles, their synthetic gas still is an order of magnitude more expensive than natural gas. So, the value proposition of replacing one of the cheapest (but dirty) fuels with a clean alternative that is much more expensive is limited. And of course the process of using the captured carbon, releases all of it back to the atmosphere. For most use cases, switching to synthetic gas would push those use cases into the deeply unprofitable region. I.e. you'd be considering many other alternatives before committing to that. Green hydrogen at the price levels they are citing is ballpark getting to a stage where it could replace grey hydrogen and be worth the extra cost just to clean up existing uses of hydrogen. So, things like fertilizer production and other chemical processes. It's still more expensive but the difference could be bridged with subsidies and incentives.