I think the main problem is that you often don't know the lyrics if you're trying to find a song. Recently a friend of mine hummed a song to shazam and it did actually work!
I seem to recall that Apple announced || demoed this a couple of WWDCs ago. I didn't realize it was already deployed. I assumed it was going to be part of Siri/HomePod.
You used to be able to Shazam the middle of a song, and it would start displaying the lyrics in real time. Apple even demoed it in a keynote. I haven’t seen that feature in a while.
Using it with Shazam would be great for when you can't understand one or two lines of a song.