"Unions" are a generic term, much like "clergy" is.
Generalizations about "clergy" do not make much sense if you want to cover Iranian Ayatollahs and Buryat Lamas at the same time. Same about unions. The context changes across the globe.
The relevant context here is that everything is done to crush any kind of wannabe unions in the united states of America, unlike say in Germany or Northern Europe.
I come from France where the desire from the elite to crush unions is also strong, but the USA is yet another level.
Given that context the unions that do exist today in the USA have been selected for their survival skills more than anything else. Like always you can only reap what you sow
Union bashing is dumb story telling to keep the taxes of billionaires low.