This, or you want to have a backup of your disk because your younger brother isn't especially gentle, or you want to have a second copy of your game so that you

This, or you want to have a backup of your disk because your younger brother isn't especially gentle, or you want to have a second copy of your game so that you can have one at Dad's home and one at Mom's. And these use-cases aren't only legitimate, in France they are even legal and in exchange we pay a tax whenever we buy a media storage device (Taxe sur la copie privée).