They serve the purpose of making sure workers get their legal entitlements.
For example, Unions right in Australia are tackling the problem of underpayment of legally mandated wages “wage theft” and have succeeded in getting a state government to adopt as policy the treatment of deliberate underpayment as a criminal matter with criminal penalties.
Sounds like you agree with me. In a democracy, unions are just about the least efficient way you could possibly address inadequate enforcement of labor laws. If all you want is a workers lobby group, then why do you think the best way to achieve that is with organisations that exploit people with collective bargaining agreements, and enforce a tyranny where nobody can be fired? Want to know why it’s so impossible to fire a corrupt cop? Unions. Want to know why incompetent teachers can last a whole career defrauding our children? Unions.
There’s no rational connection between wanting to better enforce labor laws that are already on the books and wanting unions. Democracies offer many far superior ways to address such issues.
Not only that, you seek to put words in my mouth about exploitation and tyranny.
I'd also like to point out that beyond your (in my view) irrational distaste for unions, you have a very US-centric view of what a union is. Those of us looking from the outside in are constantly bemused by people like you.
Please only respond to the things I actually say, not the things that you think I will say in the caricature you have built.
According to who? By what standard? And regardless of their current state, shouldn't workers get as much as they can for themselves, just like everyone else? Corporations sure do everything they can for themselves; IMHO even enlightened self-interest, such as net neutrality or reasonable tax laws, is not a limitation.
In economies where minimum entitlements are sufficient to protect workers from exploitation, unions serve no useful purpose at all, they are simply leveling mechanisms. Meaning the do not protect workers from getting less than their worth, they simply pull people down and prevent people from advancing themselves beyond the average. Worst of all they make it nearly impossible to fire the incompetent, which itself seems like exploitation to me, forcing the component to pick up the slack of those who aren’t.