Hey, Tom.
Businesses try to make money. That's what they are for.
The open XMPP connection for GChat wasn't making them any money. Users on GChat weren't clamoring for it. They were complaining about the spam coming through.
We didn't have enough other networks connected to make being on the federation a business necessity.
Compare email: most email addresses aren't on Gmail. If they disconnected from other servers, it would be unacceptable for their users.