Words produce Activated Concepts𓇯. I believe metaphors are so widely used because they're efficient at that: you can achieve the same activated concepts using many fewer words.
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Consider this sentence:
> Because the deadline is looming, the team has to go balls to the wall 
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Exercise: convert the same sentence into a literal, non-metaphorical sentence or sentences. I predict it will take many more words.
Then ask:
1. Are there associations likely invoked by the metaphorical sentence that are not by the literal one?
2. Do the different sentences have a different emotional valence ? And isn't a part of communication affecting someone else's emotions?
(Note: *do* sentences affect emotions is a different question than whether they *should*. See the fact-value distinction )