That language tries to conceal, heal

But even before the flexibility afforded by free verse, the line was used to restrain sense, to bottle it under such an extreme pressure that its overflow was palpable--we feel it viscerally in the vertiginous suspension of pure end, with its thrill of weightlessness, that split second before the eye returns to the left margin, and thought flows again. The line-break enacts the rift between sense and language that language always tries to conceal, tries to heal.

...

While the line-break is giving site to the incommensurability of sense and language, it's also using its capacity as a fissure to serve as an interstice through which the unsayable can enter. It cracks open the sealed facade of a finished expression and allows it to exceed itself, to emanate without the need to articulate. Ironically, this fissure is also what allows the reader to enter. It's the gesture that says, "This is not finished," with its implicit invitation to the reader to do, if not the finishing, at least some additional work. Thus the line-break is a gate; it both lets things out and allows things in. It's the point of permeability, the point of exchange between two worlds, not an inner one and an outer, not a constructed one and a real one, but simply two words that slip in and out of each other, and in the act of deep reading, become indistinguishable."

--Cole Swensen