The way there is so much successful media based on MMORPG, you would think Japan will gobble up any MMORPG that comes out like it's WoW. But not a single one of those games are even close to that status. It is a well-known fact that Japan never latched onto MMORPG like a lot of other countries did, despite Japanese companies being capable enough to produce an MMO. Their failure in capitalizing this genre is often questioned. Blue Protocol release next month in Japan, we will see if Japan likes MMORPG or not one year from now.
there is the question of vocal minority and interest in things you don't participate in:
there's a bunch of manga about random small hobbies you can have (a decent few about gunpla and some random one i saw about specifically someone roleplaying with transformers figures, but there's also the pretty common hunting focused manga, which is definitvely not an activity many people have).
you don't have to like the thing you're reading to enjoy the stories the setting allows you to tell, like, VRMMOs don't actually exist as they do in manga, there is no "full dive" technology, doesn't mean stories with that don't get written. I personally don't even play video gmes anymore, but stories about video games are always cool to me because i like having stories where people can exist in a fantasy setting but still have stuff like SOL school experiences in the modern world, those are just fun stories to me.
tl:dr, just because a genre is popular, doesn't mean the thing it is associated with is popular as it could just be something the author likes or is something that just allows for stories that people want to see, even if they don't actively participate in it themselves (especially video games that wouldn't be possible IRL (game design in manga is always atrocious, but we can ignore it because not having to think of the logistics makes the stories more fun), or the impossible wholesome online gaming experience, because you don't really see racists in text chat in these stories)