In short, they've cargo culted themselves. No wonder they've lost their place as makers of powerful processors.
Unless there is a significant cost to it, and unless the benefit is understood, there is no reason that they should be faulted as ignorant cargo cultists simply for keeping it in place.
https://www.bloomberg.com/news/articles/2016-06-09/how-intel...
> For decades, Intel’s cleanrooms have been lit like darkrooms, bathed in a deep, low yellow. “That’s an anachronism,” says Mark Bohr, a small, serious man who has spent his entire 38-year career making chips, and who’s now Intel’s top manufacturing scientist. “Nobody’s had the courage to change it.”