BECAUSE PAIN IS THE #1 WAY TO KEEP THE ATTENTION OF PUNY BRAINED BOOKWORMS.
When your heart starts bleeding because you are ridiculously emotionally engaged in a fictional story…you know you care. OH GRAPE. YOU SURE DO CARE. And the best way to show you care is to ache and worry and fret over something.
I would say that the ideal of imagist poetry which is best reflected in this poem is that poets should be able to describe ordinary objects in new ways.