I think part of it has to do with complexity. For a roadway, it must be tested within a specific temperature range and weight range. For software, it's consider

I think part of it has to do with complexity. For a roadway, it must be tested within a specific temperature range and weight range. For software, it's considered a failure if anything can break it, foreseen or unforeseen. If roads were tested like software, you could say "yeah, it supports all the common/pre-defined use cases, but we just found out it's susceptible to a jackhammer. Better fix that." And then your road would never be finished just as software is never finished.