I was under the impression that the back up to GPS for aviation was VOR:
" The FAA’s network of Distance Measuring Equipment (DME) NAVAIDs will provide a PBN-capable backup to GPS; however, for aircraft without scanning DME receivers (DD) or DD with Inertial Reference Unit aiding (DDI) equipment, the FAA will provide a conventional navigation backup service based on the VOR MON".
This is what happens at times with technology. You bank on one thing but the population or industries go another. One example, Beta vs VHS and let’s not get started on digital media changes.
Put it another way, I’d rather have the Government establish the standards for navigation and let private industry finds the means to exploit it then leave the whole thing to capitalism for in the latter you might find that the LORAN receiver you bought on the east coast may not have worked on the west (Yes that can happen, think geo-blocking on netflix).