CDs break. Hard disks crash. Phones are stolen. Sell them access to a permanent collection. You're then in the services business. That's where all computer companies want to be. A permanent fixture of everyday life.
And also the bundle importance (hence the one album per file):
The world works on bundles: a newspaper is a bundle of stories; a TV channel is a bundle of programs; a satellite channel is a bundle of TV channels; economically the world only works through bundles. The stuff you don't want pays for the stuff you do. There are sound actuarial reasons for this. It works. And artistically, we wouldn't have had The Beatles or Joy Division without the bundle.