Anybody can build a bridge that doesn't collapse, it takes an engineer to build bridges that barely don't collapse. This is hard work, don't downplay it.
On the other hand, a minor screwup in software is far more likely to cause catastrophic failure because we just don't know how to workably build large, robust systems out of code.
Nit: meeting the requirements of law isn't barely collapsing; that requirement has so many safety factors built-in because the building code has to approximate so much. The approach isn't that dissimilar from how that "anybody" you mention would build their bridge that doesn't fall down: by guessing safely.