Because right now, the big energy companies are the only ones who can create hydrogen at scale that is even remotely close to being practical in terms of cost. Unfortunately, this is using processes that are nearly as (in some case more) polluting as the ones we want to replace.

Dangle the prospect of green energy in front of an uninformed but well-meaning public; when they finally bite and commit to hydrogen, then simply switch in the gray and blue hydrogen. When anyone complains, point out that green hydrogen is still too expensive, but maybe "some day".