The problem is that you cannot figure out the actual requirements. In every non-trivial application project I had so far, the requirements (and there were lots

The problem is that you cannot figure out the actual requirements. In every non-trivial application project I had so far, the requirements (and there were lots of them) were simply not correct. The requirements the actual users created, that is. They _think_ they know the workflow. They don’t. If you don’t even ask the users, it’s even worse. But that’s okay. It is simply not possible to accurately judge how something will work until you get to use it. That goes for the creators, too. That’s why we iterate.