John Carmack's arguments against building a custom XR OS at Meta

I've written a lot of low level software, BSPs, and most of an OS, and the main reason to not write your own OS these days is silicon vendors. Back in the day, they would provide you a spec detailed enough that you could feasibly write your own drivers.

These days, you get a medium-level description and a Linux driver of questionable quality. Part of this is just laziness, but mostly this is a function of complexity. Modern hardware is just so complicated it would take a long time to completely document, and even longer to write a driver for.

Yeah this. I tried to modify a hobby OS recently so it would process the "soft reboot" button (to speed up being rebooted in GCP) and it was so unbelievably hard to figure out how to support it. I tried following the instructions on the OS Dev Wiki and straight up reading what both Linux and FreeBSD do and still couldn't make progress. Yes. The thing that happens when you tell Windows or Linux to "restart". Gave up on this after spending days on it.

The people who develop OSes are cut from a different cloth and are not under the usual economic pressures.