Here’s why. You can transform a Markdown document into HTML, RTF, or PDF and even EPUB in just a second or two. It doesn’t matter what I use to create a document; I can open it in Marked, and export it to other formats more or less instantly.
Markdown documents are just text, so you can write in Markdown on your phone or tablet – any text editor can create Markdown documents. I wrote a couple of blog posts on my phone at the hairdresser’s yesterday, for example. This morning I copied them to MultiMarkdown Composer, my current favorite Markdown editor to save as files. Then I copied the files as HTML with a couple of keystrokes, and posted them to a blog.