* To add color and vividness to their writing. Idioms can help to create a more vivid and memorable image in the reader's mind. For example, instead of saying "he was very angry," a writer could say "he was hopping mad." This idiom creates a more concrete image of the person's anger.
* To create a sense of familiarity or connection with the reader. Idioms are often used in everyday speech, so using them in writing can help to create a sense of familiarity and connection with the reader. This can be especially effective when writing for a general audience.
* To add humor or irony to their writing. Idioms can be used to add humor or irony to writing, especially when they are used in unexpected ways. For example, a writer could say "the cat's out of the bag" to mean that a secret has been revealed, even though the idiom literally means that a cat has escaped from a bag.
* To express a complex idea or emotion in a concise way. Idioms can be used to express a complex idea or emotion in a concise and efficient way. For example, instead of saying "he felt a sense of deep regret," a writer could say "he had egg on his face." This idiom conveys the same meaning in a more concise and memorable way.
Overall, idioms can be a powerful tool for writers to use to add color, vividness, familiarity, humor, irony, and concision to their writing.