It's the best way of setting up a clear goal. At my current job for a new project we only had marketing send over specs to some UX/UI designers and we're going to get the prototype UI sent to the devs for feedback. No idea what the exact goal of this new project is other than to keep up with the competition or to make existing corporate/enterprise users happy. Not the most ideal situation.

I think writing a mission statement or press release before development would sink a lot of projects before they began and save millions.