Sometimes a product is so unique, that you have to experience it by yourself. If that is the case, a press event is the right choice. Media representatives can see a product or test a service for themselves and have a conversation with the founder/developer of the product.
In this way journalists get to write and publish exclusive reports on the product even before the official product launch. By taking exclusive on-site photos or testing the product by themselves journalists are more likely to cover the event and the product itself. More often than you can imagine press events contribute to the publishing of new stories even beyond the presented product, for example by having one-to-one conversations with editors on other company-related topics during the event.