If "you have OBi devices dispersed throughout a country or the world" AND you don't have physical access and control over them, then the OBiTALK Web Portal is one possible way to access them. If this capability is not currently needed, however, there's no penalty for not using the OBiTALK Web Portal until such capability is needed.
The statement "From your single OBiTALK web portal log-in you may control your OBi devices with a great deal of granularity and control" makes absolutely no sense to me. Configuring an OBi directly is considerably simpler and less time consuming than using the OBiTALK Web Portal. Configuring an OBi directly also provides access to options and status information that aren't available on the OBiTALK Web Portal, without losing any functionality whatsoever.
If you like doing things the hard way, having less control and information available, and relying on someone/something else being there to accomplish the task, then the OBiTALK Web Portal is the perfect choice.