Why? If I pick up a phone and call my sister in Italy, or even if I call my wife who is on a different mobile network than I, we use infrastructure from different companies. But we can still talk to each other.

I am bemoaning the lack of similar interoperation between different chat solutions. Skype cannot talk to Whatsit, Slack cannot talk to IRC... Why? I don't understand it. As far as I can see, they are all different implementations of the same thing. Like different phone networks.

I say, we do not need Yet Another One™. We need to push the existing ones towards more integration. Then it would not matter which one you choose.