And what happens when a hurricane takes down the cell tower? Or the power is out for days and the cell tower's backup batteries run dry?

Decentralised radio is essentially ham radio. Individual units talking directly to each other, without relying on a single point of failure (the cell company). As others have said above, ham radio is a godsend in some situations. If you use the right bands, you can talk halfway around the world while running off batteries and using a wire thrown over a tree for an antenna.