One advantage seldom stated about being a jack of all trades (and master of none) is that it allows for a greater equilibrium of purpose and application than being singly involved in one occupation, however much money's empire forces so many to (over)specialise in one field to the detriment of others.
Is balance and the avoidance of excess not the most treasured lesson the Classical Greeks (particularly Pythagoras) have imparted us in their works and writings? Is not the best way to achieve balance, at least artistically, to try one's hand at several mediums of creative statement?
And, of course, applying one's body in physical exertion is just as necessary as applying one's cognitive faculties in intellectual labour to achieve optimal balance in the mind-body complex.
Thus the ethos of balance and equilibrium as well as the avoidance of excess in one area of life over others seems to point to the virtuous and wise path of the much-maligned jack of all trades.