There’s been a tradition of adapting poems into songs but this is often historically associated with a few select acts and genres. If it were to break into overall pop music, especially after plagiarism scandals it would be good news for songwriters and singers alike. However they’d be pickier with what they chose in finding the right one for both artistic and commercial gratification as well as avoiding legal issues.
In that scenario, a pop musician can easily get away with not writing its own songs but only because it’s an optionally necessary evil to avoid copyright infringement. A poem can be reinterpreted multiple times in any genre and can be shared between musicians without any problem. Musicians that refuse to use the public domain would become more cautious with what they write.
It’s been done before, just not on a massive scale except in the future.