I don't understand how a serious CRM with a built-in phone system doesn't already have this. Compared to Twilio — even though they're the backend provider here — there's a lot of catching up to do.

+1 to Murray's comment below. The real value isn't recreating an old-school PBX extension system, it's having a proper call destination per user: transfer a call to {user}, and the system finds them across all their devices and numbers, ringing whichever is available. That would also lay the groundwork for a real IVR for businesses that still operate that way.

This is basic phone system functionality at this point — it shouldn't still be missing.

more useful as a user destination than recreating the old fashioned pbx - i say this as someone who built and sold a cloud pbx business a decade ago. IE transfer a call to {user}, the system finds them from all their devices and numbers. Could also be the start of an IVR if businesses still operate that way