It's because it's effectively impossible to make a markdown authoring app that meets everyone's needs, and people tend to be picky about what they want in a writing environment. People have strong preferences about WYSIWYG, flavor of markdown (pandoc/quarto/GFM/etc), theming support, some want notes to be able to link to each other, etc. As an example, I require math notation support for basically everything I write which automatically rules out 90% of markdown editors for me.

All of this, but underlying it I've come to the conclusion that Markdown isn't a good format for a writing environment beyond just simple prose. There's too much left up to the flavour of it and it's got weaknesses.

I've been experimenting with using Markdown (in Typora) in place of Word, but it (and others I've looked at) have zero support for image positioning or sizing, or a way to have different (pre-defined) styles on different tables.

Which is a shame because I like keeping my documents in plain text, in version control and efficiently read by my LLMs. LyX (https://www.lyx.org/) for LaTeX is the closest to what I'm thinking of that I know of, but maybe something exists for Asciidoc or Typst.