Some software is extensively designed up front, like embedded avionics programs. The resources are made available because folks like the FAA demand it.

Why don't we employ rigorous software engineering principles to, say, iOS games? It would be a waste. It could be done, but in practice, people just don't care as much if a game on their phone crashes as they do if an airplane they're riding in crashes.

There's a wide spectrum of software out there, needing varying levels of robustness. There's not a lot that can be said about software development as a whole along these lines; inadequate design for an online banking site might be excessive design for a llama costume competition voting site.