Is software architecture really more difficult?

When they talk about software architecture here in CMU/SEI, they always say that documenting software is hard because you cannot see the real thing, you cannot draw software architecture like drawing a 3D representations of a machine or bridge. That is a myth. They say that because they do not understand mechanical or civil engineering at all.
The truth is, engineers in other disciplines also need to document their designs very carefully in various ways much complex than the three orthogonal views you may have seen in a mechanical/civil engineering handbook.

You have to calculate/simulate the force flows through a beam using a force flow diagram, you have to calculate the gear structure of your gearbox using gear diagrams, and you have to calculate the flow of air/water/oil inside the system using yet another set of flow field diagrams.

You also need diagrams at different level of detail to show how to manufacture or assemble your creation to what quality level, which could be very complicated.
Software is special because it is indeed so cheap and too easy to blow up। If we isolate every module or even function with process boundaries, like a failed component in the real world usually has, the quality of software could be much better.

In the real world, architects rarely use new/customized material or structures. They only buy tested and well understood parts and assemble/construct them using well understood methods. Software is so cheap that everyone wants to invent his version of sort/database connection, etc...

The Internet, as a whole, is quite stable because all components are isolated। A blown up file server usually doesn't crash the intranet, let alone the whole Internet. If we can somehow make that level of isolation achievable in an economical manner, we can make everyday software much more stable than they are now.