If I could provide all the keys my machine could be completely locked down and damn near impossible to break into even with complete physical access and a ECE degree.
That would require all hardware to be secure against all attackers. As soon as one attacker breaks one hardware model, they can start extracting and selling private keys that allow anyone to emulate that piece of hardware in software.
I'm also having a hard time seeing the use case. What kind of thing has hard secrecy requirements but demands so much hardware that you can't justify owning it?
The "Protected A/V Path" could be a neat feature for high security computers (consider the GPU driver, a horrible, buggy, complex piece of software, being unable to grab pixels of a security-labelled window) - but that's not what this was built for. SGX, the same.
Non-DRM use cases seem to be an afterthought, if possible at all (typically not).