Like you said, the issue is in verification by the end-user. It is trivial to provide a digitally signed (and timestamped) file. It is also trivial to provide trusted tools to verify these files. It is immensely difficult to provide a solution user will care about; which is why more often than not the most people asks companies in the data authenticity business is “can we show a green check on screen? That would be perfect!”.

And we end up with something that nobody checks beyond the “it’s probably ok” phase. If the goal is to teach the masses about trusting their source, either they have a miracle solution, or it just won’t work. (and all that is assuming people actually care about checking the authenticity of the stuff they see, which is not a norm as it is…)