It is a miracle that the web itself has survived as one of the few open interoperable protocols. Though I think this golden period will soon end, strangled by the death of net neutrality on one side and proprietary walled gardens on the other.
Ultimately, a commons is not compatible with unrestricted capitalism.
Sadly but somewhat hilariously, the thing which might prevent them a bit from offering exclusive-to-their-network content is the fact that in the US, you often don't have a choice of which ISP to go with, so if I really wanted some content which was exclusive to ATT's network, I simply can't switch off of Comcast (apartment building with no other option, past 3 apartment buildings were the same) since they've so successfully monopolized markets.
Edit: on the beginning: http://www.internethistorypodcast.com/2014/04/chapter-3-part...
I had hope for Hangouts, but Google dropped the ball big time in terms of user complexity and quality of product as they are wont to do.
I agree that video conferencing is rather fragmented but I'm honestly not sure how much that has slowed adoption. People just don't want to use video in a lot of cases. Essentially all my internal calls are on a videoconferencing system and I doubt I turn on the webcam 25% of the time. (We do use screen sharing a fair bit though.)
It is conspicuously absent on any other platform; even Android tablets can't use Duo, let alone a Linux, Windows, or macOS machine. So it's a hell of a walled garden.
Sure, bringing everybody together would be tough. You'd need a lot of discussion and probably glue/bridging code between different services. But it could be done! None of the big services are even trying to integrate with each other.