I think 'assuming that the airline has a way of preventing' people from plugging in dangerous items is doing a loooooot of heavy lifting in your argument.

How, exactly? The airlines have absolutely no way to know what shoddy electrical device you bought god-knows-where you're plugging into mains power in their airtight travel-coffin, packed with hundreds of people, hurtling across some ocean.

> Almost all the international flights I've flown have had power outlets

Seems deeply unusual to me, but I won't dispute your experiences. I've flown internationally fairly often, and in my experience power outlets are rather uncommon (at least in the eastern hemisphere, flights to/from the Americas may differ, I haven't flown around there for many years).