Cell phones are laughable single points of failure. Everyone brought this upon themselves from decades of bad engineering choices, if you consider resilience an objective. Once upon a time there was a terrestrial network of small autonomous telephone exchanges. Your phone numbers were tied to geographical locations. It seemed 'inconvenient'. Now you or your signal often have to travel hundreds of miles (as the crow flies) to find a central office that is required for call completion, even between two phones 10 feet apart. Even so-called 'land line phones' are tied into this network now because cell phone providers have remade the old Bell system in their own image and require, of all things, Internet connectivity and utility power to boxes on poles all over the neighborhood to work.

Expect it to fail all at once. You will not be disappointed. What this means in terms of the value of amateur radio is not hard to figure out.