Then the chaotic universe known as the Internet crashed Microsoft's cozy little party. The proliferation of the Web presents new challenges, like starting all over again on the issue of UI standards. To answer that question, you need to look at the evolution of the Web. Each page represented and expressed its creator's artistic proclivities. And surely you can't cripple Art with the straitjacket of standards.
Art is free-form.
And Web pages represented creativity and innovation. Those static pages started becoming more dynamic. They collected information from users and presented choices. Collections of Web pages morphed into actual Web applications. Nowadays complex programs are being built to run inside a browser.