Cable and fiber providers typically have 24 hours of battery backup in their repeaters/concentrators but no more. Most 4g/5g stations have similar backup capacity, with only a few (that will be overwhelmed) located on big enough buildings to have standby generators.

So starlink backup is still interesting if your region occasionally has outages that last more than 24 hours.

There was a major storm that disrupted infrastructure across the west coast of Ireland last year. Turned out a lot of infrastructure couldn't survive multi-day grid power loss (water plants, cell tower repeaters, etc).

Starlink is a solid backup for mitigating the risk of such disruption by having no local dependencies other than ability to power the CPE.