My guess: Fear of being accused of copying Tolkien, feeling too much like Dungeons & Dragons, or approaching any similarity at all to Rowling.
That might explain why elves are prolific in queer works, actually. I don’t at the moment have it in me to delve into what I mean, but Baldur’s Gate 3 touches on that area. Critical Role does, too. “Our elves are different” is easier to say if they’re overtly queer, even if examples have been accumulating through the past 20+ years.
As for Japan, you might notice that European (by which I’m including the UK) settings, character types, and old folklore are currently popular in Japanese media. Mangaka have been traveling for research for some years now, picking up stories that weren’t mainstream and felt fantastical.