Companies thought plumbers, electricians, etc were fungible. They didn't care which one they hired, they just needed one. There were always more in town or the next town over.

Software work appearing to be extremely fungible with offshoring and AI is all the more reason to unionize. It doesn't matter to the employer who is doing the work, so the union is the only leverage to truly saying, "hey as the person actually doing the work, I would like to be treated better, and you can't just ignore me, fire me, and replace me".

The race to the bottom already started as soon as companies saw more fungibility where there was less before. Software unions won't kick that into overdrive, they'll slow it down.