It's an old conversation, and it entirely hinges on Return on Investment (RoI). Essentially, it's the same reason why I don't make maps for the modern era. It requires more work than what I already have set up, and there's no guarantee that the work put in will turn as much of a profit as producing content for one of the larger genres. In fact, all evidence presented points to the reverse, in that the hours spent into the project won't be nearly as profitable as if they were spent elsewhere. Hence, the popular genres and systems get a wealth of material, while everything else is left in dust. That's how the vicious cycle rolls in business.
