I think it's best summed up in one part of his response.
It is a bit far-fetched, I know
Just about every airport on the planet is built in a certain way. Are you going to now train every pilot in 2 ways of doing something? Only have certain pilots that could land at this one/subset of airports? Rebuild every airport overnight?
The gasoline engine is far from the best solution for driving. Many better solutions have arisen over the decades. But the road/gas station/gas pipelines/regulatory/etc. infrastructure make it much, much more difficult than "let's just start throwing hydrogen fuel cells in every car" and everything is good.