Is hardware-based digital signing the solution to deep fakes?

To the extent that AI generated videos are already a fake news problem and that fake videos and images are expected to become even more commonplace, why isn't hardware-based digital signing being pushed heavily as a solution?

Obviously this would only work for future media, but it would be almost trivial for camera makers to add hardware-based cryptographic digital signatures to the metadata of every output file or embedded in an invisible watermark (though this raises privacy concerns).

Why isn't this being pursued in the marketplace?