AM radio costs pennies to add to a car, if it has a antenna already. The simplest rcvr to make, easily homebuilt. Still plenty of people listening to it, but old demographics. And we’ve been dealing with motor interference with AM for years, but that is where the cost lies, cleaning up the noise.
We lose the grid, and internet due to a major hack, or war with china, and satellites fail or our taken out you’ll be grateful for local radio, if anyone is physically staffing the local station. It would take me about a hour at the local AM transmitter to rig it up to provide live news. We always had back up plans to broadcast live from the transmitter, and a generator that runs for days. Same with tv, even new tv’s have tuners, no antennas provided, and few use off air, even though that number is growing due to cord cutting and streaming.
No denying that we could use the AM frequencies with a better modulation standard. Unfortunately the govt has lost interest in public airwaves except to sell the frequencies, and few listeners make it a poor investment.
But internet and cellular aren’t robust at all, and can easily be taken down.