Spotify won't play songs I have in my iTunes library

[guitarua]

Ok, so follow me here: If I own a song, whether is synced to my library or not, Spotify will not play the same song that they have on their platform. I have disconnected Spotify from iTunes library and reinstalled and it STILL won't let me play a song I already own, even if I select non-local Spotify file. All I get is : "Spotify cannot play the file right now. If you have it on your computer you can import it." Why should I have to import it if it's in Spotify's catalog?

This has happened for years....how have you not been able to fix this yet???