Programming a complex system can be achieved from the bottom up: Volunteers keep adding and sharing stuff. Old stuff becomes obsolete. The system marches on. U

Programming a complex system can be achieved from the bottom up: Volunteers keep adding and sharing stuff. Old stuff becomes obsolete. The system marches on. UI design in contrast is a top-down effort. You can't just mix and match various works from people. It's about information flow and consistency. A unified interface has to be agreed upon, and then implemented across the board. And any part of the system that fails to meet that standard, essentially breaks the UI.