Why does Shakespeare start the scene with a humorous tone as tribunes speak carpenter and cobbler?

Shakespeare does not begin the scene with a humorous conversation between the tribunes; he sets a serious but tense note of conflict from the onset of Act 1, Scene 1 of Julius Ceasar. The play opens with two citizens entering, discussing rumors of unrest due to Caesar's ambitious actions after a triumphant military conflict. However, Shakespeare does inject comic moments into the play through characters like Flavius and Marullus, trying to control the crowds before Caesar's entrance and later with the appearance of the Soothsayer who warns Caesar to beware the ides of March.