Why is Jaques considered as a moral guide?

Jaques is a melancholy character that sits in the forest of Ardenne brooding over life. Despite sounding depressed all the time, he does give smart and insightful observations about life. Sad people tend to examine life in closer detail than happy people. Perhaps his most campus lines speak to the metaphor of a play to our lives,

All the world's a stage,
And all the men and women merely players.
They have their exits and their entrances,
And one man in his time plays many parts,
His acts being seven ages.