So… back when I used Pidgin, I aggregated AIM, YahooIM, GoogleTalk, and Pre-MS Skype. What is the use case today?

I don’t even trust that. Google devices hard-code DNS and IPs and… I have no evidence or knowledge of it, but I assume that they have some Sidewalk-like ability to communicate directly to other Google devices to get outside the network you want them to be on.