To be able to either store the game disc inside the ps4 So u don't have to change the game every time u want to play another game. Or to keep a backup of the game inside the ps4 all u do Is click on it and u don't actually need the disc inside it kinda like the homebrew app I 4gt what it's called but Apple stole an idea in an iOS version that hackers made so Sony might want to do the same.