Here, we "know" that in emergencies that we will use cell phones and
the Internet, and all will be well.


Hmmm, long distance phone service was greatly reduced and no cell
phones were available in east central Alberta for a day. After the
main fiber line to Edmonton was severed. This affected some 100K
residents of the area.


One cannot predict what services will be dead in a regional
emergency. Any system that relies on lots of infrastructure
is more likely to be impaired. Ham radio, aside from radios,
antennas and portable or mobile power source (say car battery)
usually survives in enough numbers to be useful.