i have a question about why people dont make fanfictions of rwby the one on this site itself looks great but hasnt been updated in forever.

Not sure how we are supposed to answer that. I doubt anyone here can claim to speak on behalf of all the writers on this site.

I would guess that it simply isn't popular enough.

I do not like to write fanfiction.

My thought is no one here, yet, has any thoughts or want too write a fan fiction on rwby. So my idea given too you is, write one. Maybe it will go somewhere maybe not. Its your life and if you want it that much its possible.

Why write fan fiction when you can write your original work?

Because people fall in love with characters/a universe and want to further the work beyond what the author has done, or change it to suit how they would have liked the story outcome to be. This site originally started out as a fan-fiction site for the Royal Road universe. Fan-fiction is also less daunting because it is in an established universe with (possibly) established characters, so the writers don't have to develop that themselves.

RWBY is pretty niche, so it would be hard to find a fan-fiction for it on here, but you'll probably find some on fanfiction.net.