I don't think there's anything wrong with having a recognizable style

Which - duh, right? Even if you don't consciously strive for it - if you're imitating someone else, as a visual artist or a writer, your style will emerge.

But we also prize the concept of "originality" very very highly in modern art (ie since the Renaissance and esp since the emergence of 20th century modernism). Never mind that no one creates in a vacuum and we all get it from somewhere else.
So I can get it on one level - it's fanart, we're working with copyrighted imagery (so not entirely original), and it's done for free (fair use but still a somewhat illegitimate air) aka it doesn't "count" as real. It's "kids stuff" blah blah.

But all of that is true of fanfiction as well. The question my post was implying and maybe I should have stated outright was "Why do we approach/treat the two differently even within fandom?" (We say "icon dump" but never "drabble dump" for instance.)

Or I could've, you know, ask the nice, hard working admins of the icontest comms. That would have been an idea *ponders*