Because the customer has no freaking idea what the requirements are at the start of the project. I disagree. to get a scrum project (or any project) going, you

Because the customer has no freaking idea what the requirements are at the start of the project. I disagree. to get a scrum project (or any project) going, you do need to have a vague idea of what you want (e.g. I want a website to sell my widgets online) and a few features for the next iteration (.e.g. List all the widgets. Take an order by email). Scrum just says that you can inspect, adapt and iterate over that process.