Why is punctuation important in a poem?
A few thoughts...
Why? Is punctuation important in a poem?
Punctuation affects the meaning of sequences of words. If that is important to you, then some form of punctuation may be important.
In poetry, you may want to use non-standard punctuation to stress the meaning of words differently, or for dramatic effect.
Punctuation may be used in poetry to align the metre of the poem.
You may wish to omit punctuation, to allow the reader to interpret the sequence of words in different ways.