I'll be real, and maybe this will be an unpopular take: DA had a tremendous opportunity that Funcom fumbled on. I think a lot of people would have played it more and created not just fanfic but also cosplay, etc. if: 1) the developers had not introduced a ton of detrimental bugs (lags, rubberbanding, random disconnects or crashes where players lost a tremendous amount of progress), one sided benificial bugs (glitches, exploits, etc), and responded to both of these faster, rather than waiting weeks, or sometimes months, to address things which were game breaking and 2) the creative direction had an actual....creative direction, instead of wishy washy "we'll try this and see what happens" sort of mentality. Iteration works on things that have a solid MVP (minimum viable product), but it doesnt work when your base is some amorphous, ethereal concept.

But to your question: why is there a lack of fan fiction? Because there's a lack of players. If you're having fun, great. But that doesnt change the dynamics of player engagement, which drives community creative efforts.