I just joined Spotify and I think it is great. I am listening to Yoshi Ikuzou, one of my favourite Japanese singers. It would be wonderful to have many more enka on Spotify and having the karaoke versions available would be totally awesome.
Hello and welcome to the community.
Enka is fast becomming a very popular genre. Spotify adds all music available, but some labels/artists don't allow their music to be reachable through Spotify. To learn more about how this works, have a look at the music FAQ. Take particular note of the fifth point.
This applies to your second request for karaoke versions. If they are available, then Spotify will add them.