Earlier quoted context omitted.
You can't hand-wave away the fact that Gmail, Docs, and Maps are best-in-class.
Of course I can, particularly if they are best-in-class in a class that is not relevant to me. I'm not going to use web apps for email or for office documents, except for edge cases. And that is the case for most people in the world, web apps are a nicety, but not the primary use case. Maps, as I said, are different.
Even if you're not using Gmail's webapp, it's an entire email infrastructure serving as the backend for Mail.app or Mailbox or whatever you use. At this point, if someone doesn't have their own mail server, they're probably using Gmail.