I don't use LaTeX simply because LaTeX outputs pdfs. Pdfs stink in their own right but furthermore, pdfs are for printed documents and I don't use paper anymore.
What I need:
* High quality fonts and images
* Single file
* Cross platform
* Simple to create using LaTeX
* Excellent support for math
* LaTeX style readability considerations
* Massive user base
* Many extensions
1. (kinda.. if I want to use Google's font API and the browser renders it well)
2. Not a single file.
3. Not cross-platform - it will render differently on my linux desktop and mac laptop.
4. I don't know how to convert all of my LaTeX macros and workflows to HTML so I'd need something like htmltex (doesn't exist, I want it).
5. MathJax is good, but it ain't great. Too many compromises.
6. No typesetting and words per lining heuristics like LaTeX - again, need htmltex.
7. and 8. were a bit unclear, sorry. I mean in writing mathematical papers. HTML has a huge community but signal to noise for writing readable papers is pretty high. Mapping what I do in LaTeX to HTML requires many more lines of code.
Still I 100% agree that even HTML is too primitive and too inconsistently implemented for scientific writing.