It would also seem like bad business to leave it out of your niche game, unless the niche is specifically about the difficulty level. Why would you want to eliminate whole chunks of your already limited number of potential customers by only offering a very challenging difficulty?
Adding a difficulty slider is easy, doesn’t take much time, doesn’t change much about the experience, and allows more people to enjoy your media.
So leaving it out is lazy game development.
Niche audiences is fine, gatekeeping isn’t.
It would also seem like bad business to leave it out of your niche game, unless the niche is specifically about the difficulty level. Why would you want to eliminate whole chunks of your already limited number of potential customers by only offering a very challenging difficulty?