One use case where short TTL-s make sense is running a service on a residential network where a power outage or router reboot can trigger an IP address change.

One use case where short TTL-s make sense is running a service on a residential network where a power outage or router reboot can trigger an IP address change. If the IP address changes then you won't be offline for too long. Yes, it is not exactly great, but at least it works well enough for self-hosting services.