Yes, I remember they tried to expand, but it didn't catch on.

I think it may be because at it's heart Genius feels to me like a skinned/specialized Wikipedia, and Wikipedia already has other information covered. Lyrics are a good fit, because Genius has a format that suits itself well to annotating lyrics, and it is a reliable source for quality lyric content. So many lyrics sites other than Genius are horrible to look at and usually are riddled with ads and popups.