Mike Becky

Why Do Apple Music’s Curated Playlists Have Songs That Aren’t Available on Apple Music? ➝

I would guess that Apple isn’t limiting their curators strictly to the Apple Music library for the sake of future proofing. Apple hopes to eventually have all music available on the service and the currently unavailable tracks would automatically become playable once Apple acquires the proper rights. And if you own the tracks from elsewhere the playlists should already playback fine by using your pre-existing files as the source material.