Also, I can add a couple of pages of material to the start of a chapter, then skip down 175 pages to add a new problem to the end of the file. All my typesetting is done using troff. I don't have any need to see what the output will look like. I am quite convinced that troff will follow my instructions dutifully. If I give it the macro to insert a second-level heading, it will do that in the correct font and size, with the correct spacing, adding extra space to align facing pages down to the pixel if need be.
Human labor is used to do that which the computer can do better.
That would be much harder and slower if the text were kept in some manufacturer's proprietary format. Nothing, but real authors use troff. It is better than Windows. At least it has a command line interface, albeit a pretty feeble one. I would like to take this opportunity to thank Linus for producing it.