There probably is a less nefarious reason here. They built a “send this song to Alice” feature but supporting it for non-Apple services is very tough. They will

There probably is a less nefarious reason here. They built a “send this song to Alice” feature but supporting it for non-Apple services is very tough. They will need to work with everyone to integrate it. It’s possible they haven’t gotten to it or Spotify hasn’t gotten to it or didn’t bother. We don’t know.