One difference between poetry and lyrics is that lyrics sort of fade into the background. They fade on the page and live on the stage when set to music.
In the Rodgers and Hammerstein generation, popular hits came out of shows and movies.
Musicals are, by nature, theatrical, meaning poetic, meaning having to move the audience's imagination and create a suspension of disbelief, by which I mean there's no fourth wall.
I'm interested in the theater because I'm interested in communication with audiences. Otherwise I would be in concert music.
All the best performers bring to their role something more, something different than what the author put on paper. That's what makes theatre live. That's why it persists.
Art, in itself, is an attempt to bring order out of chaos.