Completing a sudoku on software which gives instant correct/incorrect feedback on digits isn't as fun as puzzling it out together. Part of the fun of sudoku is going through the mechanics, fairly.

I've heard the Souls/Bourne games described as "tough but fair". For some games, the idea is that the fun comes from beating challenges from the design of the game mechanics.

Similarly, there's fun to be had from Role Playing Games by not having magical foreknowledge about consequences. Saving, and loading to see how each choice plays out means the dynamic is "how can I get the best?" rather than "what would this person do?".