alt Hacker NewsCode needs to run on physical devices, which are prone to undervolting, bit flips, hardware bugs in specific batches, radiation, deterioration, and the like.
Preferably, I wouldn’t trust my life to a calculating device running on AA batteries while dangling from a rope.
Pace makers, dialysis machines, brake lines.
We also have fully redundant systems. The elevator for example required Otis to do this fantastic demonstration 150 years ago and now we don't think twice about it.
Do you know how elevators work now? Their safety mechanisms? Planes are 10x more likely to cause death.