The problem I have seen is when I need it most, due to a rare fiber internet outage, so does everyone else nearby and cellular data becomes saturated and unusable.
In locations where fiber is not available (like my place), cable is the next best option, and cable has a lot more unexpected downtime. I could see this being a good backup, especially for small businesses like retail shops that couldn't afford to have their POS go down for half a day.
Fiber is less expensive than and more than 10x faster than starlink, in fairness.
Our 5g towers seem to run off the fiber lines, so it’s not really a backup (and gets overwhelmed anyway).
I’m considering getting fiber in addition to starlink, but I wish they’d just buried the lines.
I see telephone trucks repairing downed lines we’d rely on many dozens of times a year. Digging a trench would probably pay for itself in a year or two.