Minimizing shipped defects is qualitatively simpler in physical engineering because the set of possible defects you have to account for is astronomically smaller.

I am a physical engineer by background but have also spent much of my career in high-reliability software systems. The problems of reliability in software systems make physical systems look like child’s play. The levels of effort are on different scales.

An important difference is that software correctness is mostly binary. In physical engineering you can usually spend a bit more money to over-engineer a component if you have any doubts or are lazy, and that works. Effort does not scale nearly as well when it comes to reliable software.