In business correspondences it is essential to express ideas, facts and expression eloquently. Furthermore as time is of the essence almost always, the shorter the sentences and paragraphs are, the briefer will be the letter, memo or notice. Thus it saves both the reader's and writer's time, a commodity which is invaluable.
Business people are busy, a huge amount must be read every day and their is neither time or cognitive ability to dedicate to deciphering prose. If you state your points clearly and quickly with no drama and just the facts it stands the greatest chance of being understood and taken on board... Sadly this advice is rarely heeded in the real world.