CDs are a standard storage medium containing audio encoded in a standard way. There are a multitude of ways to get that content (the audio) off of the CD and playable in a multitude of ways, because the music is in its pure digital form.
An iOS or Android app, on the other hand, is architecture-or-platform-specific code, depending on a particular OS-sized API and all its UI libraries, all of which are expected to become obsolete and unusable in a relatively short time.
An iOS or Android app, on the other hand, is architecture-or-platform-specific code, depending on a particular OS-sized API and all its UI libraries, all of which are expected to become obsolete and unusable in a relatively short time.