Usually it‘s about standing, resources and options. Serious problems like fibre cuts, local power outages and DDoS attacks are usually not in their scope and they have to wait for 3rd parties to fix these problems with little iptions to speed up those processes. Bigger ISP usually have teams/departments which have well established processes/solutions to tackle these problems. That said, I‘m totally aware that each of them (small or big ISP) have their pros and cons - as always it mainly depends on your use case and requirements.
