Here's why:
* Poems often have a different rhythm and structure than prose. A period can feel abrupt and disrupt the flow.
* The lack of a period can leave a lingering effect, encouraging the reader to contemplate the poem's meaning. It's like a pause for reflection.
* Many poets believe the poem's ending should be self-evident. The final line or stanza should be clear enough to signal the poem's conclusion.
However, there are exceptions:
* Some poets do use periods at the end of their poems. They may want to emphasize a sense of finality or create a specific effect.
* If the poem is part of a larger work, such as a collection, you might follow the publisher's style guide.
Ultimately, it's up to the individual poet to decide whether to use a period or not.
Here's a good rule of thumb: If you're unsure, leave the period out. It's more likely to be considered acceptable than using a period where it's not expected.