If a game is so hard that the player gives up, they won't buy your next game. That is an existential threat to your game studio.
Worse though, if your game is deemed 'unfair' rather than just 'hard', then even the hardcore gamers will avoid it. That's enough to kill the business before you even start the next game.
Some studios pick the 'hardcore' market, especially once they've built a reputation and a following, but everyone else needs a more general appeal in order to stay in business.
If your studio's only goal is to make money and games are a byproduct then it makes sense, but in most of the gamedev it leveled itself out some 10-15 years ago - very few studios outside of mobile gaming target the lowest common denominator audience, most seem to understand that opinionated design adds flavor and sells the game as well. Certain target audiences simply never cross under any circumstances, it's not even necessarily "hardcore vs casual".