Hmmm . . . Back when I read BtVS fic, I always thought it stood for the "N" in "NC-17." But "naughty" fits too.
It may well do, in that fandom. But in FoLCdom, because of the emphasis at the time on nfic being romps and there being very few of the serious, angsty long nfic we have in the mix now, it was naughty and it did fit.
Nowadays, not only does it not fit the angsty stuff, imo, it also doesn't cover the nfic that has no sexual content, but is rated above PG13 for violence, non-sexual adult themes etc.
So it jars a little in my head these days. But, if I don't think about what it stands for (which I rarely do), it does okay.
I'll bite about the quote, because I think the question of why fanfics go towards "NC-17" territory and why people like them is a loaded one.
And, like all reasons why people do things, an incredibly varied one, too. I don't really think it's possible to give one definitive answer on that.
LabRat