>never mind that most crashes are caused by humans, very rarely by technical issues going amok

Because humans are the fallback for all the scenarios that the tech cannot reliably cover. And my intuition says that the tech around planes is so heavily audited that only things that work with 99.999...% accuracy work will be left to tech.

That's so incredibly reductive, that I'd go ahead and call it plain wrong.

"Caused by a human" is the lowest tier, first base human instinct analysis of any accident, and as such, unless proven otherwise, can be discarded out of hand.

It comes down to: if a human mistake is capable of causing an accident, your system is badly designed because it assumes a part of the system known to be unreliable (a human) is always reliable.

The whole trick is designing systems that are safe despite humans being in the loop. Then you get to benefit from the advantages humans bring over machines without suffering the downsides.

Still those technological issues do happen, and in those situations it's good to have a human pilot in control. See for example Qantas Flight 72 - the autopilot thought aircraft was stalling, and sent the plane into a dive. It could have ended up very badly without human supervision.