‘A concession is not required from the loser for the winning candidate to be sworn into office. Instead, they’re merely a political norm that provide a sense of closure for both campaigns. A concession is nothing more than a means to foster a peaceful end to a months-long (and often, as in this case, bitter) campaign. However, that doesn’t mean concessions aren’t important. Not making a concession speech could still have serious repercussions…’

Source: Lifehacker