> Real question: Why do you think Intel does this?
I'm not sure large traditional silicon vendors like Intel, TI, et al re-evaluate the documentation requirements (and costs) on a chip by chip basis. It's probably done by chip class and for companies who've been selling chips by the millions over many decades to industries as diverse as defense, aerospace, automotive, etc there are classes of chips where robust, complete documentation is not only expected but often a required part of the RFP, compliance or conformance processes.
While this level of effort probably isn't needed for every chip in that class, it could be hard to reliably predict when a general purpose chip is still in the design phase which customers may be interested in it during its life (which for some of these chips might be decades). Many chips which conform to MIL-SPEC or other similar standards which can require extensive documentation are simply enhanced versions of standard chips, so the docs exist anyway. Finally, there's the organizational capabilities and culture aspect. Once the org needs to maintain the systemic ability to generate serious documentation at scale, you end up with a lot of managers and staff who think this way.