My wife edits etc books, had a bit of a chuckle when I said that the text just flows automatically.
The problem is that people use Word. For a few dozen pages it works, you get 800 pages of text, pictures and maths then it screws up big time on a regular basis, every few hours. And recovering is not an easy or quick job. Seems Word also doesn't understand multiple files per book, it all has to be in one huge, 50MB, file. Crap. Why not use another wordprocessor? Well, ask the author, you get what you are given and Word unfortunately is it.
Then you get authors who lay an equation out using spaces and underscores and smaller font sizes for powers.
Doesn't seem to have progressed beyond what Ventura managed a couple of decades ago.