Sitting on a cell phone tower is highly discouraged in this part of the country, may be different in other parts.
But there are usually at least two towers involved in any connection. And there could be a signal strength/quality problem in either one. That tower's connection to the wired system could be swamped by other users or maintenance.
Then there are the problems with reception inside buildings, especially those with more metal construction or near wiring. Not to mention (although I'm about to) the azimuth alignment of the phones antennae with any disruptive/reflective objects as well as the tower antennae.
It all boils down to a very low powered radio signal and those kinds of signals are far less stable than other kinds of physical connections, even if that might be a string between two cans!
Most cell phone transmitters have an automatic, self-starting generator built in. But those require fuel and and don't always start when needed.
WARNING: Further afield opinions follow.
Most of us seem willing to ignore these 'events' until they reach our own level of frustration. So far, those levels seem to be lower than the suppliers desire to improve service. But that may just be my cynical opinion. I wondered last week, when one hand at the cable company said my modem was bad while the other said the hub was being repaired so a new modem wouldn't make any difference, what would have happened to their highly advertised 'phone' service during the outage. Just seems follish to allow any one company/technology have too much control in our lives. Now, that, of course, doesn't apply to
government...!