Markdown-UI started as a inspiration to teach my son about programming. Being a father I was looking for ways to teach my child on how to create websites, as a primer to make it easier for my child to understand the basic concepts (i.e. container contains elements, grids have columns and rows, types of buttons, etc.), without spending too much time necessary for other quality activities and important matters.
For the developer standpoint, Markdown-UI helps the developer to focus on the big picture on paper or text-editors, and with few details it lessen the cognitive load which means having meaningful productivity which equates to developer happiness.
teaching kids about programming
creating responsive UI's for mobile and web
easily communicating your UI
rapid prototyping
focus on important stuff
UI/UX brain-storming sessions via email, whiteboard, text editor, paper, etc.
shell-scripting your UI's