Why would anyone want to write an opera libretto? The words are generally held to be at the service of the music, relegated therefore to second place, so what would make any self-respecting writer choose to offer up their skills to the peremptory demands of a composer?
The reason is probably quite simply because it's something else, another way of stringing words together that can take them into an entirely different dimension. Any writer with curiosity will want to experiment with their chosen form, to try more than one way of exercising their craft. And music can take words to places that they cannot reach alone.
Langston Hughes knew what the two could do together:
And he knew what he was talking about. He crafted a performing text – some of it sung, some of it spoken – from a play by Elmer Rice, in a collaboration with Kurt Weill that resulted in Street Scene, that extraordinarily powerful piece of music theatre covering an explosively hot day in the life of a New York tenement in the 1940s. For Weill, this was the only way to work, bringing together creative artists in an active relationship to forge something new in a 'true amalgamation of the arts' that for him was the meaning of theatre.“Cheap little rhymesA cheap little tuneAre sometimes as dangerous As a sliver of the moon.A cheap little tuneTo cheap little rhymesCan cut a man'sThroat sometimes.
As there are no hard-and-fast rules as to what makes the best basis for a libretto, so there are no grounds to prove that a particular sort of writer will make the best librettist. Some of the most successful operas have texts that are based on plays; David Belasco's Madam Butterfly and The Girl of the Golden West for example, Georg B