Unfortunately karafun, like so many other systems, has egregious holes in its catalog. I hate playing the “this song? No… this song? No… this song? No…” game.

Psst... if you sign up to their Premium tier you can play songs from their "Community" (i.e. user uploaded songs). If you sign up to the "Pro" tier, you can play even more songs that are normally locked from their catalogue (but you'll have to manage rightsholders authorization yourself).