Answer: "Because it wouldn't have mattered."
Before I made the plunge and decided to form a startup, I read everything I possibly could about the process... what to do, what not to do, etc. I knew all the mistakes first-time founders make, and I was pretty sure I'd be able to recognize the issues and avoid making any of the really big ones. I didn't expect to get it all right on the first try, but I was certain that I wouldn't get it all wrong.
Guess what? I still made pretty much every mistake in the book. Almost every single thing that I'd read about basically went out the window as soon as I began.
Why? Because once you and you alone own something and put it out to the world to be used, judged, loved, hated, it becomes a very emotional and very personal experience. And once emotion enters the picture, it's very hard to step outside of yourself and assess the situation logically and pragmatically.
When you work for a large company, it's very easy to distance yourself from the product you're building, because most of the time you are not the only one involved in building it. You shipped a buggy piece of crap? Yeah, it sucks, but it's management's fault because they set an unreasonable schedule. And that contractor that worked on that one part didn't know what the hell he was doing. My stuff worked great.
But now this product is your baby. And when someone tells you it's ugly, you're almost certainly not going to be able to take a good hard look, and say, "You know what? I can see where you're coming from."
This presentation is great. Every single point is true. But speaking from experience, having someone tell you about lessons learned isn't the same as actually learning those lessons yourself.