Most people now rely on their cellphones for telephone communications.
Years ago, people had wire landline phones in their homes. Even when the electrical power went out, the phones still worked because power was coming from the central telephone office. Even if they have a desk or wall phone in their homes today, most are Voice over IP (VoIP), which will only work if there is electrical power in the home.
Thus, we have the general population relying on cellphones for their voice and text communications. Those devices, besides needing to be charged, are only as good as the cell towers that they communicate with.
See this article on the situation that has been experienced in the California Fires and is easily replicated in any earthquake situation, Cellphone Outages During Fires Preview Life After a Big Quake.
A quote from the article highlights the fact that redundancy in power for wireless company cell towers is not a given, "There are no federal or state regulations that mandate cell carriers have any backup power for cell service, said Ana Maria Johnson, program manager with the Public Advocates Office, an independent organization of the California Public Utilities Commission that advocates on behalf of consumers."