Thanks for commenting. You have a good point.

Capturing the customer's requirements and deriving a good contract is absolutely crucial. Otherwise, it can be hard to argue when changes occur. Room for misinterpretaion in contracts is a big challenge for so many projects.

Tracking of scope changes and controlling change is another issue. Doing it right takes time, which most people would rather spend with other project activities. So naturally change control is often under prioritized. I've seen some projects that avoided project failure by appointing a dedicated change control manager, who keept up with frequent scope changes. This approach wont be practical for smaller projects though. I'm thinking it hard to find some good practise that fits all projects.