For those who are like me, and have only just begun building their startup, if's enormously useful to sit down and do a few takes of an impromptu video, and answer each question on the application.
It is almost like an outside opinion asking the right questions to critique your idea and your determination. It allows you to think about your ideas and the challenges you'll face in ways you may not have before. Basically, it forces you to bring your idea down to earth from the clouds and think critically - and realistically - about it.
I second any opinion claiming it's worthwhile to fill it out even if you're not funded for this exact reason.