[jaredklewis]

But even if they did all the look the same, how would that be negative?

How terrible would it be if all your desktop apps had completely different UI components? Indeed, people seem to greatly prefer desktop apps that follow the style and UI conventions of their OS.

So if the Internet were largely made of pages powered by a few popular UI frameworks, I really think it would be a huge boon to users everywhere. UIs would be more familiar and consistent. Seems like a great step forward.