Short phrases in poetry are used to increase the flow of thoughts so that the poem takes on a synergy as it is being read.
As the reader move quickly form one line to the next with new ideas expressed in each line, she experiences a rush as the poem flows by.
Short phrases paint multiple pictures in reader's minds that shift rapidly as each line is read. They often contain poetic devices such as consonance or cacophony.
This is how someone's day may start:
Ching-chang sounded the clock
Take stock announced the radio
Tick tock replied the clock
Thump bump and rise to the new day.