The philosopher José Ortega y Gasset asserted that "clarity is the courtesy" of the true philosopher. I would like to add that conciseness is also the courtesy of any writer. When I get longish (really longish) messages, I wonder if the writer ever puts himself or herself in the shoes of the reader. Can it really be that verbose and excessively lengthy ruminations are worth the time of the reader?
The Gettysburg Address was short. The parables of Jesus are short. So, if even Lincoln and Jesus were concise, why should you and I not try to be concise? I am also willing to bet that concision and brevity are the admission fees to genuine insight and creativity. One artist tells us that "creativity is subtraction," meaning that what we take out is as important as what we put into a work (see point no. 10 in the above image). Enough said.