It would also be trivial for them to ad, as several third-party builds support it and a couple patches have been offered over the years. It's almost certain there's a business/policy reason they don't want to support it.

Sharing a PC's wired connection via ad-hoc WiFi is still a pretty common use case. Mesh networking for communication in emergencies would be an awesome use case, but it depends on a lot of people using it for most of its benefit, and the installation procedure starts with "first, root your phone".