Have you actually read the article? That is literally how it first started for XMPP.
And because there were far more Google talk users than "true XMPP" users, there was little room for "not caring about Google talk users". Newcomers discovering XMPP and not being Google talk users themselves had very frustrating experience because most of their contact were Google Talk users. They thought they could communicate easily with them but it was basically a degraded version of what they had while using Google talk itself. A typical XMPP roster was mainly composed of Google Talk users with a few geeks.
And once google separated completely,
As expected, no Google user bated an eye. In fact, none of them realised. At worst, some of their contacts became offline. That was all. But for the XMPP federation, it was like the majority of users suddenly disappeared. Even XMPP die hard fanatics, like your servitor, had to create Google accounts to keep contact with friends. Remember: for them, we were simply offline. It was our fault.