The sense of play.
Using language with an eye to beauty and to form allows a writer/poet to have fun in a way that approaches language and writing as connected but separate things.
The flows of poetry give the writer access to chance utterances that surprise, awkwardnesses that tumble across prepositions and meatier words toward meaningful happy accidents, to drive the purpose of a poem home to its reader through language as well as the page.
Only poets get to make serious and regular work of matching phonemes, morphemes, consonants and vowels. Only poets get to constantly concentrate on setting up rhythmic patterns just to break them into disarray or to balance them out until sound and form act as one unit.
Visual poetry, for me, allows for even more of those fine touches.
I mean, you can have a graphic novel about Batman sitting in his bat-cave or you can show him swooping across rooftops.
With visual poetry, the rooftops are yours.
You can emulate a sunset by giving text the appearance of settling under the bottom of the page. You can do what Mallarme did in “A Throw of the Dice” and make it look like an object is rolling across page after page. You can make an explosion of words, phrases, lines, ideas like Douglas Kearney.
You can put together a human image and make it look ironic, silly, beat down, or super strong. The possibilities of what can be shown are only limited by imagination, which should only be limited by the expanse of this cosmos.
For me, visual poems are the most fun to write because they can exist between and within speech and writing.