This is a relative new concept where the requirement is for a IP connection at all times, which in turn is a technology many airlines do not have installed. Some areas in the world are not as well covered by the satellite constellations as others, depending on supplier, airlines operating in these theatres may not benefit as much as those operating in the well-connected world.
Depending on the location and theatre of operation, this technology can work very well reducing the usage cost and congestion on the VHF. Looking forward to implementation