Relive, retry, repose. The three reasons for saving.
Once games became larger than a normal human’s reasonable play time frame (and I said normal. People who can finish Resident Evil in Insane mode three times in a row just with the pistol need not apply), the save feature became a must — mostly because it wasn’t feasible to wrap the game up in a single seating.
That is repose. That’s when you save the game because it’s time to go. Because you’re tired. Because you’re bored, even, but just in case you want to try some more… This is the rationale behind games like Legend of Zelda or Nethack – games where saving is merely a method to ensure you can continue some other time.