Evacuation notices can be, and are, announced on AM radio during emergencies.
Having lived in disaster prone areas, people tend to be glued to the TV and radio before, during and after to get updates on the situation. TV and the internet are the first to go with the power, and even if you have a generator, that doesn't mean your internet connection will work. Radios will.
I don't think the OP's point was that SiriusXM was being used for emergency coordination, but the lack of a traditional radio in the car forgoes the existing emergency radio infrastructure.
Having lived in (and still do) disaster prone areas, people often don't even own radios outside of that thing they get annoyed by when their car turns on before bluetooth/Android Auto/Carplay connects and don't bother with any way of watching TV that doesn't involve the internet.
Pretty rare to have people actually listen to AM radio or OTA TV for a massive chunk of the population.
I was in a disaster zone without internet (or electric, except for my car) for two weeks. You are right, but neighbors end up sharing information pretty quickly when their preferred means of communication (ie internet, mobile phones) stop working. (AM radio still worked and could be received from a great distance, and TV might have been working, but I'm not sure because I didn't have a generator for the first ten days and after that it was for refrigerator and clothes washer.)
Having lived in disaster prone areas, people tend to be glued to the TV and radio before, during and after to get updates on the situation. TV and the internet are the first to go with the power, and even if you have a generator, that doesn't mean your internet connection will work. Radios will.
I don't think the OP's point was that SiriusXM was being used for emergency coordination, but the lack of a traditional radio in the car forgoes the existing emergency radio infrastructure.