When I write a poem, I try to put line breaks in places where the reader would pause, however briefly, before continuing to the next line. I want the end of a line to be a place where the reader can quickly comprehend what has just been read, and besides, writing the poem without any line breaks would turn it into a prose poem. And prose poems, to me, have a completely different feel from poems with line breaks.
So the line breaks in my poems are, I guess you could say, “resting places.” They’re not for visual effect. :)