I wouldn't say I use one on a regular basis, but they do have their uses. For a longer document, things like footnotes, internal cross-references, and an auto-generated table of contents are pretty darn handy. For something like a book, add endnotes and an auto-generated index. These things are painful to do in raw HTML/Markdown/whatever. No LaTeX editor I've ever used, and I've used several including Lyx, is much better. They get a little better with something like a WYSIWYG HTML editor, but that's really a word processor too. It's just a lame one, hobbled by the lack of abstraction between the interface and the output format. Really, word processors do this job better than the alternatives because it's what they were designed for.
BTW yes, it is possible to write longer-form documents like this while remaining technical. Junior folks can focus 100% on code. More senior folks still code but also get asked to teach and explain stuff, and after teaching or explaining the same stuff a dozen times putting it in writing starts to seem like an excellent idea.