Woo hoo. Somebody in the FAA is getting huge kickback checks.
Actually it’s about cost. With GPS, all the FAA needs to do is publish the approaches. Other navaids require maintenance of a lot of infrastructure.
Actually, the antiquated ILS glideslopes are beginning to be replaced in other parts of the world. Hanging on to those expensive dinosaurs if only the US and a few other countries still use them is unfeasible in even the medium run.
You have it exactly backwards. Kickbacks from Raytheon and others have held this at bay for three decades, with success due in part because cheaper GPS systems enable things like drug runners maiing instrument landings in a field someplace at night and in the rain.