There is plenty of greed on both sides of the equation.
I do believe unions forced some good changes; workplace safety is one of those. I also disagree with the idea that businesses mostly made or would have made these changes on their own with only an economic motivation.
However, now that these things have been accomplished, I think the primary goals of labor unions are power, money and political influence. The economic effect of the labor union is the same as any other cartel/pseudo monopoly: higher costs.
The long-term net effect of modern labor unions is that prices are higher and quality is lower. Mediocrity is protected. Businesses are held hostage.
The day of the beneficial labor union is over.
My father, RIP, was a union guy for 40 years but had a contracting business on the side. He worked extremely hard on both jobs. He railed against the union workers that were "loafers" and the fact the union protected them. He never saw {and nothing I could say would change his mind} the irony, in his position. The same could be said about his politics. Too bad, he was a smart guy, but FDR was his version of God. Forget logic, didn't work.
...and business goes offshore, which deprives Americans of jobs... and whole business sectors are hobbled (eg. manufacturing)... and incompetence is rewarded (eg. government employees)... and workers are forced to contribute to causes and candidates they abhor... the list goes on and on.