So what's wrong with Remote Assistance? Who knows, but apparently, MS support isn't allowed to use it:

Bright and early Saturday morning, the reader called the Windows support number. "I was glad that at least my case ID was still there, but I still had to confirm every detail one more time," the reader wrote. "The Windows support tech I talked with sent me an e-mail with three links -- one to download an installer cleanup utility, and others to install .NET framework and upgrade it. He was very good and we were done in ten minutes. Then I asked him two questions. How come this procedure is not in the knowledge base articles? He developed it himself, he said. Since I had problems copying and pasting URLs from multiple lines in his email message, why does he not use Remote Assistance? Because Microsoft does not let them."

That's just.... interesting.