Understanding IC's to repair them is a failing prospect. They are black boxes by nature. If you can't actually repair it without the factory, why should they write you a manual to help you repair it?

Beyond that though, there is a degree of Power lost through dispelling the blackbox (information asymmetry is Power, never forget). Explaining how it works opens up PR doors places would rather not have to deal with, and cuts off avenues of development that companies in the space thrive on. See Nvidia graphics cards for an example. Nvidia doesn't "sell" you the card, in the sense of allowing you to do whatever you want with it because they can't. They are contractually required to hide implementation details around things like HDCP and the in hardware foundations of many streaming related DRM technologies.

Then you have other aspects, like their move to requiring Nvidia signed firmware to access the power control of modern cards. This ensures only their driver can feasibly compete in the market and locks out any potential competition that may be able to pull off a true innovation using their own hardware platform (see nouveau and the signed firmware issue).

All of this would be undone by actually being required to support user firmware implementation, and disclosing how everything works.

https://docs.nvidia.com/drive/drive_os_5.1.6.1L/nvvib_docs/i...

The above is a link to an offering for a self-driving processing offering (therefore safety-criticality somewhat justifies the absurd guarantees of firmware lockdown), but my experience tells me that once ypu nail down a tricky process like that, you worm it into as many parallel business vehicles as you can.

Just knowing another company is even capable of doing something like that is a signal of demand to competitors. Hence the desire to hide everything possible as no one else's business.