And they evidently spend very little time on the things that would actually improve the lives of their users in macroscopic ways. The fact that our dominant model of an operating system is essentially c + shell is a tragedy. The operating system does almost nothing for us to help write fast, correct programs in a reasonable amount of time. It is of course for this reason that unix itself has barely improved in a material way in 30 years except in these kinds of microbenchmarks. Third party tooling and languages have of course improved, but largely to cover the gaps that the operating system has largely failed to address in a meaningful way.
Um, when the PC computers switched from real mode to protected mode operating systems, that was an enormous boost to programming. It's hard to understate it.
But writing at that level of specificity for an entire system greatly increases creation and maintenance time costs. You may lose the opportunity to make future performance improvements as a result.