I don't know if there is a hidden /s but I disagree with your general statement. Music Videos often enough expand the story the song tells.
While "The Blaze - TERRITORY" is already a beautiful song to me, its music video[1] Always brings a tear to my eye.
That said, music Videos, like many songs themselves, are not rarely meaningless and bland. I guess that is just the result of commercial music.
They do not, they add nothing. And if they do then the song is bad.