There is a strong bond between Music and Text. Perhaps the strongest bond we have in the arts? One might even say that music without text is a relatively new invention. And while immensely meaningful to some of us, perhaps this is a rather small cult?
Using rhythm and repetition to memorize the kind of information that creates society and culture is a natural impulse - music elevates instruction and knowledge, thus creating religion.
Many composers have fallen under the spell of words - once you turn to opera, you can't go back. I can hardly think of any composer, save Mozart, who was able to navigate easily between the worlds of text/music and music alone.
When working with a text, form might be a given. Finding the right vehicle for musical expression is a struggle - creating architecture that allows an educated listener to take in the whole of an art-work - not only as a string of moments - has been on composers mind throughout history. This has lead to development of musical forms such as the fugue and sonata-form. Once you work with a text, however, you might find yourself freed from the need to organize your thoughts in such structures. This is appealing to me as a composer.
Another element of setting text is the opportunity to analyze a text on a deeper level. I would say that you probably don't really know what a text means to you until you have set it to music. As you work, connections appear where even the hundredth reading saw none. A few years back, I wrote a mini- one-man opera on the Norwegian folk-tale "Askeladden som kappåt med trollet" (Askeladden who had an eating contest with the troll) and was utterly surprised to find that my music naturally was sympathetic to the troll and found the protagonist to be a little too cocky...
When Monica asked me to set "After Death" by Christina Rossetti for Concerts in the Heights' concert themed "Love in Times of Alienation", I found the poem to be about as depressing as anything I had ever read. The music that emerged to accompany the words was however not entirely dark, but carried with it at least as much sweetness and nostalgia. "Death" and its relatives "lay", "slept" received a simple, static line. The "I" person is set to a gentle lullaby that is on occasion appropriated by the man who did not love her. He has his own music, which also associates with all thing living and growing; a dance - typically experienced from afar.
A man - much wiser than I - was asked: "Why do you like poetry?" and he answered: "It gives me what I don't have." This is true for all the arts, and while the reading of this poem in and of itself mostly depressed me, the act of setting it to music brought me a healthier combination of defiance and resignation.