When it comes down to it, we write poems to encapsulate something we want to remember and share. Something important enough we want others to know about. We could write an essay, but they are too dry. A short story is too complex. Your message may get lost. At the same time a short story has parameters that you can’t go beyond. Short stories start in the middle of something and as soon as the problem is resolved, the end must come.
People give a piece of photography advice. If you have a picture book of a vacation or an event, show people only a handful of selected pictures.
Think of the person you are showing the pictures to. With a whole stack, people look, but their attention is drawn to the next picture. They want to know if they next picture will be even better.
But if they have a known quantity, let’s say six, then they know what they have. They can study the picture and savor it. Especially if they know you edited your pictures down to a few. They can attend to them all.
Back to the short story. We read a story; we enjoy the world created by the author. But the writing is to spur us on. Keep us reading and we want to know what it is next.
However, a poem is selecting a picture from the photo album that tells the whole story. It is up to the reader to spend time with it and discover what you have to say.