My suspicion is that the vast majority of people who search for lyrics don't care about song meanings or annotations. Azlyrics does just fine, which is why they've always been at the top. If people wanted song meanings they would search for song meanings.
My theory is that RG wasn't able to grow as fast as they hoped and have to resort to these methods. How else can RG justify a $15 million investment? Their biggest competitor, songmeanings.com, is bootstrapped with only a couple employees, which shows the true market size of the song meanings / annotations market.
Remember that most consumers want things that are insanely simple and give them immediate satisfaction. I'm not surprised that most people on HN think otherwise as they tend to be deeper thinkers than the average consumer.