In reality, large-scale events happen every year at unpredictable locations and at unpredictable times. Public Safety agencies have to be prepared to respond to such events as they occur. To do that they need effective communications capabilities even if it means keeping a low-usage system to assure its availability when the time comes that it IS required. Today, unused frequencies are being sought for commercial use, hence any frequency that is not kept in some use will likely be lost and therefore unavailable when it is vital. Operational personnel decry the potential loss of FCC allocated frequencies for Public Service because of managerial 'bottom dollar' focus to the detriment of community protection.
Individuals pay for insurance for years, sometimes decades, before it is 'cost effective'.
With government, emergency communications systems are insurance for the future.