Comment by orangea

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.