Why should you avoid the use of sarcasm clichés and idioms in business letters?

A business letter should be concise and to the point. It should clearly state why you are writing, clearly present information related to the matter of the letter, and state what (if anything) you want the recipient to do in response to the letter.

Idioms and cliches can obscure the point of a business letter and sarcasm can put the recipient in a negative frame of mind.