A lot of them are really corrupt. In slovenia, unions are very friendly with some political parties and unfrieldly with others, and the "other" one proposed a tax change, which would basically lower the income tax by raising the zero-eth tax bracket level (progressive taxes, 0% for first X eur, then 16% for the next bracket, 26% for the next,... X was to be raised). This would mean that someone earning minimum wage would pretty much pay zero income tax... the unions were against the proposed change, because this would mean that the government would get less money.
That's fair. Unions can be corrupt in the US too. If they get greedy, they can take down the company (manufacturing can only compensate up to a certain point depending on international compensation).
I have started believing in unions more over the years because I work for a company that is well known for doing the right thing and caring. Yet, I've repeatedly seen the company break its own policies and screws people over. So I feel the issue is pervasive if this is really a "good" company.
It could be that contracts without a union could fix my main complaint - not consistently following the rules. But the only way to force this is through legislation or unions. Unions seem to be more feasible.
We were a communist country (yugoslavia) and there were always unions here... but as with everything, all the union leaders were in the party, and did what the party wanted them... same with the company directors... so yeah.
But it's funny, because a lot of left parties here (even the ones with the red star in the logo) are always saying that we should tax work less, and tax capital gains more... but then the "other party" does that, and they start protesting (probably because they hope to be in the government after the elections, and want the money to steal for themselves).
I remember hearing about a union in China and thinking the same thing - how the union is basically government run instead of run by the members.
In the US, for years the corruption was organized crime controlling the labor unions to extract money for themselves mostly through "protection" from them starting strikes.
I mean.. technically the unions here are independent... but we all know which way they lean. If it was an organic movement, voulounteers and all that, then sure. But with the amount of money they get, and the amount of work they (don't) do, for me personally, it's not worth it.