Wow. For once I don't agree with the people going after Microsoft.

One of the big advantages of tying the browser into the OS is that programmers can make other apps that integrate IE's web site rendering.

Apple does something similar with Safari. There are lots of apps that will display web sites or web-like content, and they use the rendering built into the OS.

Of course, Microsoft could remove the browser, but leave the rendering engine in so that those third-party apps could still use it. The engine should be part of the OS, but the browser doesn't technically have to be there.