I ask this all the time; I hesitate on the brink of something wondering what the point/outcome might be. I'd be so much happier with a crystal ball some days!
It's a great question to ask - as long as it doesn't become the reason itself to not act. "What's the point?" is a sensible question when asked sincerely. Ask it with a sigh and you'll soon discover how much easier it is to stay on the fence/couch/sidelines.
Sometimes, we do it because we need to prove we can. Because the answer is "why not?". Because we don't always need to know a perfect outcome. Because we must. Because we are compelled. Because the only thing holding us back is fear and that's never the best reason.
Unless it poses a moral, ethical or physical danger, why not challenge your assumptions and those of your mentoring circles... Ask why do it? And maybe do it without a perfect answer.