Creator of Marvel comics Stan lee comments on Iron man film –
I think I gave myself a dare. It was the height of the Cold War. The readers, the young readers, if there was one thing they hated, it was war, it was the military. So I got a hero who represented that to the hundredth degree. He was a weapons manufacturer, he was providing weapons for the Army, he was rich, he was an industrialist. I thought it would be fun to take the kind of character that nobody would like, none of our readers would like, and shove him down their throats and make them like him … And he became very popular
so as per the creator it is the decision to made a weapon manufacture to be liked by everyone.Only way to do is revealing the Iron man identity as tony Strak
Now coming to the film point of in first Jericho missile test scene we can see tony is looking at his own weapon in hands of evil man
Later in a charity event he was reported that his missile have been found in terrorists hands and we can see Tony slowly transforming at that point
this is end scene where he reveals he is iron man .Although he is a narcissist ,self obsessed ,egocentric billionaire i don’t think that he just wanted to Show off in reveling his identity .
My representation is he wants to tell the world that he is not a weaponry war monger but he has more to him.the only way to say that is revealing his identity. in the scene we can see the pain in his eyes
Another representation is Tony is not man like other Super heroes who carries emotional baggage.After his parents death he heavily traumatized and went to a path of self destruction to avoid the pain. So he is not a person who can hold the deepest emotional distress to himself .May be he thought it is better to reveal his identity instead of carrying this burden himself secretly