Think of the prologue like a film trailer, Shakespeare uses strong words and language to draw the audience in. He gives us just enough information to engage our interest then tells us that if we want to know more the next two hours will fill in the gaps.
Shakespeare's choice of words can seem depressing, but it also lets the audience know right away that this is a tragedy. The problems are not going to cause some inconvenience to the characters, but lead to their death. As an audience we are more conscious of the choices made by the characters because we know that their choices will lead to their death. This dramatic irony heightens the suspense throughout the play and intensifies the tragedy as it could have been avoided.