What difference would it make if, Shakespeare decided to end 'Hamlet' with "the rest is silence"? Do we need to be introduced to Fortinbras? And are the instructions For Hamlets funeral important? If so, why?
Hamlet is one of the more complex of Shakespeare's tragedies. Many people have questioned whether the subplot involving Fortinbras was necessary at all, which explains why many movie adaptations omit it completely. First, it is worth pointing out that Shakespeare's tragedies rarely if ever end right after the death of the hero. Macbeth, Julius Caesar, King Lear, and Romeo and Juliet are all examples of this. Second, Shakespeare's plays typically end with a speech by the highest ranking character, which is Fortinbras in Hamlet, since he is now the ruler of Denmark. Beyond convention, though, these last few lines allow the audience a sense of closure. They depict Horatio carrying out Hamlet's wish of retelling the truth of the tragedy. They cement our belief that Hamlet was indeed a tragic hero -- noble in most respects, but with a flaw that lead to his demise. Essentially, without these lines, the play would have no denouement to speak of.