The on demand resources allow the OS to efficiently store only the resources that are needed. As you play through a game with 100 levels, the system can delete

The on demand resources allow the OS to efficiently store only the resources that are needed. As you play through a game with 100 levels, the system can delete assets from earlier levels to make room for new assets for later levels. Effectively this makes it less likely that a user will delete your game as storage fills up. More work, but ultimately good for game developers on the platform.