Yeah indeed, that was my feeling on it as well. As much as Linux et al might get in ones way at times, what we get for free by relying on them is too useful to ignore for most tasks I think.
That said, perhaps at AWS or Google scale that would be different? I wonder if they've looked at this stuff internally.
There certainly are times OSs get in the way. But it's hard enough to write a good database, we don't need to maintain a third of an OS in addition.