Well, one explanation is that a lot of non-fandom dedicated sites with roleplaying often involve a more kink-based component to it and less of a focus on the writing and stories themselves, unlike RPN whose community in general has more focus on the stories and writing.
Oh, you misread me. What I meant was, fandoms don't get overwhelmed by furries, while RPN-like sites do, as they aren't as narrow. However, on RPN I have never seen a furry RP, and I find it surprising, since such open communities are usually dominated by furry RPers.
Well, in my experience, RPN-alike website (story-focused, yes) are, in fact, dominated by our fuzzy friends. Shrug.
Maybe this place is just magic, idk.