I was originally reading on Literotica which had a story (I forget the exact name of the story) which led me here. As to what led me to start writing, it was the collaborative aspect. Instead of having to write a full story myself, I could continue a story from where someone left off.
A long-time roleplayer and I've had it on my mind for quite some time to put some of my ideas and fantasies into their own stories, especially since I already have a few developed OC's. Particularly for some of my more niche fantasies and kinks - of which there's not much of, even in story and erotic literature form. So a sense of "filling the gap" in a genre, as well as the thrill. More specifically, it was another roleplayer advertising their story on here that introduced me to the site itself.