If anything, the impression I got at my last job where I was in the union was that the union negotiations mostly created an excuse for not increasing individual pay. "Sure, you perform really great and all, but if we give you more we'll have to reduce pay for someone else based on the agreed upon average increase."

For high-in-demand jobs such as SWE, the leverage of "if you don't maintain competitive pay I'll probably start look around for other work" is much more effective than union negotiations when no one is paid bad enough that they'd be willing to go on strike to get better terms.

Education is good and free enough that the supply of qualified labor would be hard to keep down without governmental intervention.