A press conference, formally defined, is the convening of the media for a specific announcement. Press conferences can flop resoundingly. First of all, reporters hate 'em. Journalists want to be first with the news. Since everyone attending gets the same information at the same time, the possibility of reportorial initiative is lost.
Journalists are also busy with daily deadlines.
So the necessity of schlepping cross-town to a meeting that may contain little news is often a royal pain in the butt. If the answer is yes, scratch the press conference. On the other hand, executives inside an organization often think in terms of press conferences, because they picture themselves as important officials ready to reveal important news to the world. Frequently, their thinking is delusional. But, if you work for them and they insist on a press conference, you often have little choice.