The fundamental difficulty is the blue sky nature of software. You can literally code anything you can imagine. Language semantics, algorithms, architecture,

The fundamental difficulty is the blue sky nature of software. You can literally code anything you can imagine. Language semantics, algorithms, architecture, it's all up for grabs, it's all cheap, and the applications are unlimited. Compare with traditional engineering disciplines where you have massively constrained costs, materials, and even goals. What would civil engineering be like if instead of the immutable laws of physics you had a system designed from the tiniest quark up to the largest galaxy by humans, and if that design was subject to change on a whim?