I imagine they shut down analog cell networks sometime in the same time frame as analog TV, maybe before
Analog cell phones died like the buggy whip. As more 2.5 generation cell phones were sold in the early 2000s (with more features), desire to change to digital phones increased and hits on analog cell towers dropped. When that happened, cell providers began to removed their analog receivers and transmitters on towers and turning off their analog networks and simultaneously stopped selling dual use (digital and analog capable) phones in stores. It was simply a feature driven technological evolution in the early 2000s.
As for digital TV, that was forced upon us by the government. There was a deal made to sell the analog TV frequencies in the 600 and 700 MHz bands to cell phone providers to increase digital phone bandwidth but only after something like 70% of all people had purchased digital TVs. DTV sets were expensive and weren't selling. The change over date promised to the cell companies was extended several times. The FCC auction for the analog TV bandwith went for $19 BILLION. But, since digital TV sets were not selling so the phone companies, having paid billions for the bandwith and needing it badly, forced the government to put a drop dead time on analog broadcast TV, in June of 2009. From that point on, analog TV went dark.
