@Reconstructo,
A philosopher must necessarily pay attention to his words, since he is attempting to articulate an often new position or concept using older or more common definitions. Most are extremely careful about what they write, and make the attempt to write with as much clarity as the subject permits.
In some respects either the style "is" the philosophy, or at least follows a particular philosophical method. Spinoza, following what seemed to him to be the best method of mathematical deduction, reads like geometry, and with purpose. JS Mill, or Descartes choose a more personal style and diction, as if to say that anyone even untutored in philosophy can make sense of what they are saying. Nietzsche, one of the great prose writers in German, took his writing seriously despite (or because of) his literary style.
To say that all philosophers should be brief seems to be saying at the same time something about knowledge and the way it must reflect the truth. Yet truth, such as it is, seems neither obvious nor simple, but rather a very complex notion that requires the use of many perspectives and many different voices in attempting to reach an understanding. Plainsong or Gregorian chant is one approach to musical vocality, but there are also the full choruses of Handel or Verdi to be cherished for their own visions.