Enjambment is important in poetry because it creates a sense of flow and continuity between lines. Because of this, enjambment also helps poets control the rhythm and pacing of their poems, creating different effects, like urgency or tension.
Also, by allowing thoughts and phrases to flow seamlessly from one line to the next without pause, enjambment can play with expectations and invite multiple interpretations.
In short, enjambment allows poets to add depth, rhythm, and complexity to the structure of a poem.