But you will have just spent months/years promising people you were going to improve an aspect of their life (through your business solving their problems, or maybe through getting more financial independence for your family etc.), and you were unable to do so. In many cases you've been trusted with extremely important things. You will have been trusted with a leadership role (in society, not just a company), and you will have failed, regardless of the value of the experience. Startups don't really get traction (outside of social) without serious contributions: being involved in solving hair on fire problems.
So, let's say you're starting a banking/commerce related startup like PayPal, and some fraud happens on your network which ultimately leads to it failing to gain trust (though it is relatively secure) and thus failing to gain traction and failing. Sure, you may handle the breach well, and go on to have a high paying job as a security analyst or something based on your specific experience.
But good luck trying to raise capital again. Good luck getting your friends and family to support you and take you seriously when you're going down your second "I'm quitting my job to give everything I have to a startup." Good luck recruiting engineers who know you as the ex-CEO of failed startup XYZ, etc.