Also why no one really appreciated ISDN over here in central Europe. Yes, there are ways to do better _now_, and it would have been trivial to support channels with better codecs by negotiating something different than u-law 8kHz PCM, but back then that resulted in rather good quality. The issue was that few people got ISDN phones, which resulted in them using analog outputs on an adapter device, which got later incorporated into the internet router, which at one point switched from ISDN to VoIP. And people plug a phone via an analog jacket into the router, instead of using a VoIP capable phone or even anything digital. While many do use DECT cordless phones, those rarely use the DECT hardware inside the router, and instead use the one in the charging dock, which itself connects via an analog, POTS-bandpass-filtered, phone jacket to the VoIP router.
Oh well, we will probably never get that kind of quality, which is only possible with QoS on the whole path, if there is any congestion. That is the one thing something like rocket.chat and discord can't provide.
Edit: the way to do this is to force quality upon people, wherever you won't drive them away with the cost this incurs. That way people will associate your brand as a whole with the quality, i.e., in that case, people will associate AT&T with quality, not AT&T premium.
Normal people do not even know what kind of plan they are on, except for about one hour before and after they sign the contract.