Word makes the world go round. Perhaps specialized publishers will accept LaTeX, but most of the industry does not. Writers need to plan to transmit their manuscripts in DOCX format and to receive notes back in the same format. Of course, something like LibreOffice may be compatible enough, depending on how comments are handled.
How does one write something like a math textbook in Word, I'm curious how it's even possible. Do you handwrite every single formula in the point-and-click UI, wouldn't that be extremely time consuming and expensive?
Probably anyone publishing a math textbook would be happy to receive LaTeX files. Math book publishers are a tiny part of the publishing world.