I believe it’s a holdover from older oven technologies. Like gas ranges with an always-on pilot light and manual gas on off pipe valves you were supposed to close before travel. IIRC those were the origin many historic city fires in dense housing, and the reason for a lot of current gas safety like the sulfur/bad-eggs additive that makes unburned gas an lot easier to detect.

But nowadays the worst that awaits those who return after forgetting the oven is generally… just a bigger utility bill instead of losing everything and maybe killing people.