- On any device as long as it runs a browser
- You can write TeX documents as a single file with ease
- Phones are not designed for reading, so dynamic layout or not, it will still be inferior to finely typeset document
- With care so can be TeX; carelessly written HTML docs will be just as bad as anything else
- CSS is a pretty poor layout tool; typographically speaking, CSS is very subpar to TeX's capabilities, using JS... well how much better is it than just using macros in TeX/LaTeX?
- markdown is fine for simple stuff but for highly complicated documents involving lots of generated tables, lists, and mathematics it is almost like having no tool at all;
- but many people DO like printed documents (I rarely can stand reading anything but basic technical stuff on screen, say language reference is fine but anything that requires thinking, has to be printed);
TeX is not locked to pdf in any way (it is not even it's native format). HTML's support for formulas is primitive (the only decent tools available are ... based on TeX). Academic world is not entirely uniform either but while I do think LaTeX is not ideal (TeX is though), I simply shudder when I think about Word or any MS or Adobe products.