I think that stems from the developer's intent. Making a hard game easier waters down the journey the creators intended, but making an easy game harder only adds to the experience. Like, the 2D Mario games are generally really easy, but there's still lots of value in those games. But then there's the bonus stages which are generally really difficult, and that adds even more value to the journey.
Then on the other hand you have From Software's games, where the creator has said many times that the experimentation, adaptation, and the subsequent deep sense of accomplishment cultivated by the difficulty is a key part of the experience he wants his players to have. (There's also the sense of community that comes with helping others with advice or cooperative gameplay) Relieving the player of the difficulty with an "easy mode" only serves to water down that experience.