Can someone who has written novel-length fiction give an explanation of why you need specialized software? I've never written anything longer than a short story

Can someone who has written novel-length fiction give an explanation of why you need specialized software? I've never written anything longer than a short story (on MS Word or Notepad) back when I used to write fiction. So I am not aware of the problems that accompany a longer work. I always thought if I started writing again I'd use vim or Sublime Text. I've heard things like being able to do outlines or charts or whatever. But those things seem to lend themselves better to handwritten notes or hand-drawn diagrams.