I find it really hard to explain the (life-changing) utility of plain text syntax for writing, so over time I’ll post some different analogies. First Attempt (it’s all downhill from here): Markdown and Fountain allow you to assemble the panini before you put it on the panini press.
Traditional rich text, paper-page-based writing software like Microsoft Word and Final Draft is like making a sandwich while it’s hot on the press. You’re constantly having to peel apart goopy cheesiness to get in some other ingredient you forgot/decided you wanted to add later.
Markdown/Fountain is like assembling all the fresh, crisp elements of the panini and working with/reassembling them until you’re happy with the construction, then you pop it on the press and voila! (or in this case “eccola!”)
Bonus MAGIC: Even if you’ve already popped it in the press, you can pop it back out of the press and it’s refreshingly cold, crisp, and restackable again.