WebRTC seems comparatively low-level, and I'm not sure it would support the basic use case for webex, gotomeeting, etc.: i.e., conference calls with audio, screen-sharing, and (less importantly) video of participants.

We use GoToMeeting (Citrix), and find we also regularly relay on the ability to call in from a regular phone, so this has become a requirement.

Customers calling in, anyone non-technical who's having issues getting the web client working (even the technical folks sometimes have trouble with it... they have a Java applet install/launch client software), or anyone with a flaky internet connection need this (that last one seems to happen quite frequently whenever anyone is traveling...).