I use apps other than Evernote on my Android, iOS, Windows and Mac devices to create and manage Markdown documents. This means that almost no documents that I create are created, stored or managed by Evernote. And the number and variety of my Markdown documents is increasing rapidly.
Having to use multiple platforms to do one thing is frighteningly inefficient. Evernote is available on all of my platforms and it needs to fully support Markdown.
In other words: For me, Creating, previewing, exporting and managing Markdown documents needs to be an Evernote capability.