Three things come to mind: (1) imitating higher-status individuals may give you reproductive advantage by getting you access to a larger pool of potential mates

Three things come to mind: (1) imitating higher-status individuals may give you reproductive advantage by getting you access to a larger pool of potential mates. (2) fitting in with the herd may be beneficial in short term because that way you don't have to think for yourself (of course becoming a lemming has disadvantages as well...), (3) sharing emotions with others may help group cohesion (people develop trust of each other by observing and attempting to predict each other's behavior; the people typically deemed to be most trustworthy are those who are both friendly and easy to predict, think dog/man's best friend).