Part of the fan-studies stigma is, I hate to say it, perpetuated by academic hierarchies. Of course it’s a chicken-and-egg phenomenon, but it’s hard to break out of. So many fan studies scholars—many of the people doing the most interesting, crucial work, are adjunct or non-TT (tenure track). I do see this changing.
Anne is right, but it is a generational thing. Adjuncts are young scholars, as they age they will bring fan art into the discourse. I have watched this happen over the years in Mechademia.