I just watched a video that covered this in part. You want to keep the player immersed in the game experience. The more interfaces you give them, the more they’re taken out of the experience.
So autosaves are a great way to keep the user interacting with the game and feeling immersed.
Pet peeve, games that won't let you save
I wish all games would just let you save whenever you want to! Why is using checkpoints and auto saves so common?...