The common safety architecture in heaters and small appliances seems to use a resettable thermostat for normal temperature control, plus a thermal fuse that opens permanently during abnormal overheating.

Why is the backup usually destructive rather than a manual-reset thermal breaker? Is the one-shot behavior mainly meant to prevent anyone from re-energizing the appliance before the root cause is inspected, or do thermal fuses offer a reliability, placement, or failure-mode advantage that a resettable cutoff cannot match?

I’m asking about the engineering design choice, not about bypassing or replacing a fuse.