When expressing mathematics, you want to focus on the formulae and underlying principles, not styling and layout. TeX provides a design spec inherently to stand

When expressing mathematics, you want to focus on the formulae and underlying principles, not styling and layout. TeX provides a design spec inherently to standardize and provide consistent published mathematical content. HTML abstracts layout less, and TeX gives you more mathematical creative expression. I personally like using HTML5 as a rendering engine, and TeX as the "design" spec. I built LaTeX2HTML5.com a while back for this purpose, so I could build all of diagrams and mathematics in TeX, but publish to both HTML5 and paper.