This may be good advice for an instruction manual or children's books, but I think good prose is something of an art in and of itself. Some of the most successful writers do the opposite. Look at the articles that go viral ..you see that the prose is varied and even complicated, not just simple.
The best prose is that which conveys the intended message for the intended audience in the best way possible. I think it's also a revealed vs stated preferences problem. People state they want/like simple writing but revealed preferences show otherwise.
I think the reason why so many business authors give this advice is confusing cause and effect. Writing simply does not make you successful or persuasive, but that people who are involved in business write that way naturally, but success at one does not follow from the other. Just like Bill Gates did not get rich by being good at bridge.
The best prose is that which conveys the intended message for the intended audience in the best way possible. I think it's also a revealed vs stated preferences problem. People state they want/like simple writing but revealed preferences show otherwise.
I think the reason why so many business authors give this advice is confusing cause and effect. Writing simply does not make you successful or persuasive, but that people who are involved in business write that way naturally, but success at one does not follow from the other. Just like Bill Gates did not get rich by being good at bridge.