Holla, Hamlet, SAY WHAT?

Generative questions for Act 5, Scene 1

What is Shakespeare attempting to convey to his readers about the purpose of life with the construction of such a rueful scene between Hamlet and Yorick's skull? If life ultimately results in the reduction of humans to "chapless" (5.1.91) and skulls - unmarked by previous feats and distinctions - what is the point of living a productive or successful life? Is Shakespeare in advocation of a life marked by legacy, or does he maintain the cynical notion that everything is meaningless? What does that say about his role as a playwright, or one who thrives on the immortality of his words?

In response to Hamlet's question concerning how the gravedigger is able to "sing in grave-making," Horatio suggests that "Custom hath made it in him a property of easiness" (5.1.67-72).
What does Shakespeare convey about his view on life through the detached nature of the gravediggers, and the way in which they are able to sing despite their morbid setting and task?
Are there any other seemingly odd events/qualities that have appeared throughout the play in which the idea of "habit" overrides their eccentricity?

Is Gertrude's sorrow toward Ophelia's tragic death genuine?