Itunes Store Library Different than Apple Music Library

I buy songs from the Itunes store pretty regularly. I’m not subscribed to Apple Music because I don’t like the idea that I only get to keep the music I download for as long as I keep paying that monthly fee. I would rather own the music permanently.

I discovered that the library of music available to purchase at the Itunes store is different than the library of music available to download on Apple Music. I was searching for the acoustic version of “Times Like These” by the Foo Fighters, and it came up as available if I subscribe to Apple Music, but not when I searched for it in the Itunes store app.

I pose this question to whoever at Apple decided this: Why? What is the point of having a song that is ONLY available through Apple Music? Aren’t Apple Music and Itunes both owned by Apple? Why would you not want a song available to purchase? I would have purchased it if it were there, but because it wasn’t there, I didn’t spend any money on it. That means Apple lost money. So why?