Although, designing against physical attacks is very difficult, so I guess there’s no need to imagine a good-hearted conspiracy of conscientious hardware folks.
There is a reason why a lot of system integrate the security processor on the same piece of silicon whose state the security processor is meant to protect.
The reason discrete TPMs exist is supposed compliance with crypto standards, and physical protection against key extraction, but they sort of miss the forest before the trees. What matters to users is the protection of their data, not the TPM's secrets, and discrete TPMs arent very good at the former.
But there’s a pretty big social harm to locking people out of their devices, like the generation of tech-illiterate kids growing up that haven’t been allowed to break their computers well enough to learn anything about them.