"they are otherwise useless"
That's simply not the case for the most common mechanical components or engineering constructions. Bridges are fully functional without software. The same goes for buildings (and the majority of components that make up a building including stairs, doors, windows, walls, floors, thermostats, lighting, etc.). Even cars, which have software integrated to regulate many functions are still driven primarily by basic mechanical functions (ignition, combustion, power transmission, suspension, power generation via alternator, etc.).
At a more fundamental level, all components related to mechanical advantage that are so prevalent in our lives, yet mostly forgotten (gears, screws, levers, pulleys, wedges, etc.) are not being replaced by microcontrollers or actuators. You'd be hard pressed to find a better software+electronic component solution to solve the problem that the screw solves.
I assure you, I love software far more than I've ever loved mechanical engineering, but it's naive to think that it will overtake (or even come close to being more critical than) fundamental mechanics. Aside from information and communication, software only serves as a proxy for control over our physical world. I guarantee you that if you were to take a look around, the amount of pure "stuff" derived from basic engineering greatly dwarfs that derived from software.
While we could live in a shittier version of our world without software, we couldn't live in a world without traditional engineering.