They might seem baffling or random to you, but most idioms were born hundreds of years ago, and have slowly become part of everyday English speech. Because idioms add imagery, using them can make your writing more memorable.

What they convey can be conveyed by other words, but only with lengthy sentences and with more words. You can also use idioms to: You can also use idioms to: Express Complex Ideas … Idioms enliven speech, so native speakers use them frequently. However, idioms can make someone sound like a native speaker, and communicate a feeling or attitude toward an event in a way that literal phrases cannot.

In essence, idioms and phrasal verbs are widely used in the entertainment industry and academic set-up but strictly in personal documents such as informal essays and articles. Idioms are phrases (groups of words) that have a hidden meaning which isn't clear when reading the words literally. Idioms and phrasal verbs can be applied when: writing stories, books and articles that are only meant for entertainment, writing plots for plays, movies and other acting scenes, writing poems and songs. A sentence such as “She said it was time for him to have a taste of his own medicine” could be easier to remember because the reader can relate to the act of taking medicine or to the displeasure of a bad smell or taste.
Idioms and Phrases They drive the ideas of the author in a better way and with few words. Without the use of idioms, a foreigner speaking English will never "enter the spirit" of a foreign language.
Idioms are a type of figurative language that can be used to add dynamism and character to otherwise stale writing.