[samueldr]

Thinking about situations [...] > where this is objectively bad

Thinking here about a smartphone. Note that I'm explaining the current state of things, I am *not* excusing the state of things.

Directly for end-users, generally no real scenario where it's bad as long as they can enroll their own keys in a safe fashion preventing evil-maid type attacks.

Tangentially for end-users, locked devices are easier to make worthless for thieves. FRP on Android, or whatever Apple does, when it's locked to a user account even when reset. This is one thing that would become harder to implement when the root of trust can be manipulated on the device.

Then there's supply chain integrity for OEMs. This is the reason some android vendors only allow unlocking when attached to an online account after a delay (e.g. xiaomi). Some unscrupulous vendors would open the box, replace the system image with a malware-ridden system image, and sell those to end-users.

Finally, there's somewhat a case for DRM and similar uses. The current implementations are built on the current "security" model, where it's security for the businesses first, then security for end-users last.

Still, I agree wholeheartedly that users should be in control of the root of trust, in a way that does not reduce their abilities to use their owned devices. Add to that that standards-based boot should be used. All the time. All devices.