The cheapest source of hydrogen is hydrocarbons, i.e. oil. So I doubt the "oil companies" care.

My experience with hydrogen gas, in semiconductor manufacturing, is that they like to leak. Special fitting that are not cheap are needed. Last I heard about hydrogen fuel cell systems though is that they were working on a matrix to store the hydrogen that would alleviate the leakage issue and the claims of "remember the Hindenburg".

As for an ICE losing power on hydrogen, that really depends on the implementation. If you try do do it like an LNG conversion with a mixer where the carb goes then yeah, you get about 80% of the gasoline powered version's HP due to hydrogen displacing about 29% of the air in the air/fuel mixture going into the combustion chamber.. But if you direct inject it the 100% of the air goes into the combustion chamber and you can gain up to 15% more power than the gasoline version.