Your first assumption is wrong. Food and water are necessities, of course, but you can survive without either for days (outside of extreme weather environments) and they're also very portable. Communications are an urgent and ongoing need, for military actors and civilians. Without them you are not only in a bad situation, you have little idea of where to go. Military communications manuals contemplate up to 5 levels of communication for different contexts, from wraparound digital services to smoke signals and the use of secret symbols for identification/navigation.

You are right about communications infrastructure, which is a favored target in any militarized conflict. Mesh networking offers a workaround to communications breakdown, albeit at the cost of bandwidth and deployment effort. LoraWAN devices are quite cheap at the margin (under $10 in bulk) but hardening, powering, and installing them is labor-intensive, to put it mildly.