Here's why:
* Purpose: Formal letters are typically used for official communication, such as business proposals, legal documents, or letters to government officials. They carry significant weight and require a tone of professionalism and respect.
* Audience: The recipient of a formal letter is often someone you don't know personally or someone in a position of authority. This calls for a more formal and respectful approach.
* Structure: Formal letters follow strict formatting guidelines, including specific greetings, closings, and use of titles. This formality extends to the language used.
Other examples of correspondence requiring formal language:
* Academic papers
* Legal briefs
* Official complaints
* Letters of recommendation
While other types of correspondence may require some degree of formality, formal letters are the most demanding in terms of language.