Hi,
The benefit is persistence between loading, and yes when you start the app, the logic of this particular game may simply not even query this playerprefs at all.
typically, if your game is well made or complex, it should remember the last state it was open, and so you'll find that in complex systems relying on PlayerPref is essential and become part of the logic mechanism entirely, it's not always needed, but something to consider. In the case exposed, I don't know if the game can be resumed directly in the loaded level or in another level, hence the option of using PlayerPrefs which solves both cases.
Bye,
Jean