Why do poems rely on imagery to convey abstract concepts

I think poems rely on imagery to convey abstract concepts because they allow the reader to visualize the true meaning of ideas by say using another say process that is similar. This could be like talking about how tough life is economically after 4 years of depression in mining right now and that waiting for work and income to come is like looking at a tree in winter when it looks dead and then seeing it in the spring when its buds open up and its blossoms bloom forth into a blaze of color. 

The answer is "he was bad enough in all conscience, but the devil himself could not temp him to turn slave-trader. satirical is a synonym for sarcastic. so when the author says that tom walker could not be tempted by the devil he does not literally mean "the devil" but he means that he is too morally upright to become a slave-trader.