Writing long documents in Word is painful to the point that people prefer to stick to old tools like FrameMaker.

It's also painful in a different way than LaTeX. While LaTeX is complex but deterministic, Word just eludes your efforts in a way that does not build a coherent mental model but rather a loose set of fuzzy rules learned via frustration.

I deeply believe that this was by design and is in general part of Microsoft culture, creating a separation between programmers and users to make them suffer in their own ways. No wonder Bill Gates became a philanthropist in his later years. He knows better than anyone that future historians will figure out all the evil he expertly inflicted on the world.