The drive would not work on any other PC.

It is a de-phase of strategy. You see, TPM was devised by Microsoft along with Intel at a time when Windows wanted to tie down users to subscriptions. The idea was that an onboard TPM would allow an encrypted BIOS (UEFI secureboot) and a wholly encrypted disk. The upside for MS was that one Windows license would be tied to the hardware. So, you couldn't use a key, however valid, with another piece of hardware. And if anything in your hardware changed, your cryptographic keys would change, then you would have to buy an entirely new Windows license (or migrate your old one to the new one, that was never established) because MS wanted to make W10 the last version and it was all going neatly into a subscription. So you wouldn't be able to move drives to new hardware.

But then Azure happened.

MS got a new CEO and a new strategic vision were an OS wasn't their main driver but B2B cloud sales. That engendered the concept of “W10 is practically free”. At the tail of the 8.0 and 8.1 debacle, MS wanted people out of those versions as soon as possible, so they gave free licenses to anyone who upgraded, even if they upgraded from a pirated copy. So now TPM is everywhere and W11 uses it for encryption, but the main motivation isn't there anymore. And nobody sees the point of secureboot except for very specific use cases with laptops. And TPM can encrypt the whole thing but, as you quickly devised, if anything happens to it, you lose all your data, so why would you unless you work for the government or something.

Essentially the tech is here, but the use case for which it was devised doesn't exist anymore. It's a piece of tech that only few enduser wants. But now it's mandatory for everyone.

TLDR: it's vicious DRM that MS wanted to impose on everyone, but kinda got lax about after backlash and change of strategy.