A straight line drawn with a ruler might be equivalent to "as per our phone conversation I'm enclosing...", yes, but anyone can also draw stick figures or poorly proportioned outlines of people, and I'd say that's what's equivalent to most of the bad!fic on ff.net or Ao3...

For me, even though I would call myself a better writer than an artist (and writing is certainly my main medium), I actually find it easier (and faster) to draw something passable than to write something passable.