Re: So they force him to use Word hmm?
Most publishers want Word documents since that's what their office staffs are used to working with. Same with the writer's agents, copyeditors etc. That doesn't mean the writer has to compose their text in Word, just that there needs to be some kind of output TO Word format at the end of the composition process. That format could be as simple as .txt though or even .rtf as long as Word can swallow it.
Classically manuscripts on paper were submitted in a publisher-specified format, large margins and double-spaced lines for pencil editing notes and corrections, monospaced font such as 10-pt Courier to make word count easy, author name and book title on each page in case the loose paper got floor-sorted, that sort of thing. Old habits die hard in the publishing industry.