>>712739298
I can only assume it's a combo of Digimon World being a game that's really niche, so there are not enough people who want to make one. And 80% of Digimon fans aren't fans of that game, so fan projects don't get enough encouragement. Also, a world 1 clone is a significant undertaking for one person to put together. Most Digimon fangames are V-pet sims for that reason.