Not only did Facebook and GChat refuse to peer with little players, they refused to peer among the big players too. We could have had something like IRC for the masses, peered chat servers with bring-your-own-client. Instead, we waited decades for iMessage to get Android support which only happened long after everyone moved on to IG, Messenger, WeChat, etc.
Email is probably one of the last great open[ish] distributed systems we’ll ever see. There are just too many incentives to build walled gardens instead.