If we took the same approach to other engineering, we'd be constantly tearing down houses and rebuilding them just because we have better nails now. It sure would keep a lot of builders employed though.
This is almost exactly what happens in some countries.
If the residents die and someone new purchases the land, the old house is (generally) torn down and a new one built.
On the other hand Microsoft and taceboook did collude to keep salaries low. So who knows.
It was more tech companies in collusion than many people realize. 1) Apple and Google, (2) Apple and Adobe, (3) Apple and Pixar, (4) Google and Intel, (5) Google and Intuit, and (6) Lucasfilm and Pixar.
It was settled out of court. One of the plaintiffs was very vocal that the settlement was a travesty of justice. The companies paid less in the settlement than the amount they saved by colluding to keep wages down.
https://www.mercurynews.com/2014/06/19/judge-questions-settl...
I do not think it is the only reason. The world is complex, but I do think it factors into why software is not treated like other engineering fields.