Why did tony stark tell the press that he is ironman at the end of the movie?

Tony told the press he was Iron Man because...that's just the way he was. Throughout the movie, Tony had defied other people and their requests, and Tony definitely liked toying with the press, so when Rhodes told him to stick to the cards, he decided he had a better idea. Like someone said earlier, if you waited through the WHOLE credits, you would have seen a scene with Samuel L. Jackson as Nick Fury. Jackson then asks Tony if he would like to join the Avengers. All in all, a great movie!