Elon's first startup was CMS software. Not all that sexy either. And he did that until he was 28. It's easy to think he's godlike, but he didn't get to work on space ships when he was 22.
Many people enjoy this website and just because someone tried to add wind into someone else's sails don't mean it's your job to tell them to stop inventing and dreaming because they're not somewhere glorious.
I hope gizmo is the first person to land on Mars and I hope just to spite you they start after they're 30...
The people who are revered here (justly or not) are people like Steve Jobs, Bill Gates, Elon Musk, Richard Branson. All in their 40s and 50s.
And yes, if you're going to do a startup you might as well do it in your 20s (all of the people above did!) because you have fewer responsibilities when you're young, and when you're older you often can't afford to put your life on hold.