I think that a comparison with Engineering is not that helpful for software.

Software has 0 construction cost but that it does have is extremely complicated behavior.

Take a bridge for example: the use case is being able to walk or drive or ride a train across it. It essentially proves a surface to travel on. The complications of providing this depend on the terrain, length etc etc and are not to be dismissed but there's relatively little doubt about what a bridge is expected to do. We don't iterate bridge design because we don't need to know much from the users of the bridge: does it fulfill their needs, is it "easy to use" etc AND because construction of a bridge is extremely expensive so iteration is also incredibly costly. We do, however, not build all bridges the same and people develop styles over time which they repeat for successive bridges and we iterate that way.

In essence, cycling is about discovering more accurately what is wanted because it is so often the case that we don't know precisely at the start. It allows one to be far more efficient because one changes the requirements as one learns.