There's no interoperability between services. We really don't have a video calling standard or anything. It's great that you can use 50 proprietary services, but have you ever called anybody without asking "Do you use Zoom/FaceTime/Teams, etc?" No, you have to get in touch with them before hand and arrange the video call or install some client application. You can't just give someone a number and make a video call like you can with a traditional phone. Nobody ever asks me who my cell phone carrier is to make sure we can make a phone call.