There’s also competition aspect. Full iOS/Android is required to be relevant in the market, so all mainstream smartwatches integrates equivalents to literally late 80s supercomputer in them. There are exceptions like Xiaomi watches, but they’re low-end, low margin options.

I think it’s plausible that none of operational nuclear warheads were designed with supercomputer clusters more than half as fast as the latest Apple Watch. Resources packed into watches are that plenty.