Free services and better terms from a union that you don't pay for because you know that you will most certainly get all the benefits of the collective bargaining, ugh!?
Because unions need lawyers (and other professionals) to litigate on their behalf. The Venn diagram between lawyers and iron workers/developers/journalists etc. is very slim. So money is required to hire this skill set.
However workers who represent the union are often unpaid. Or paid very little for their efforts.
There was a very recent Supreme Court decision that impacts this - employers can insist (as a condition of employment) that employees use arbitration only for these kind of claims. Which makes class action suits impossible, and leads to more and more wage theft - since stealing $1000 from a bunch of employees would be enough to warrant a lawsuit if done collectively, but not if each individual has to go through arbitration.
> Always wondered why aren't (some) unions free, staffed with elected volunteers? Perhaps like a floss project.
In the US, unlike in most other countries, unions usually receive exclusive rights to representation. Decertifying a union is technically possible under the law, but almost impossible in practice, so there's no competition between unions for membership the way that you see in most other countries.
That gives the union very little incentive to keep its fees in check, because there's no risk of members defecting (they're legally required to pay) and essentially no risk of its members choosing to be represented by a different union.
What, so in the US people doing a certain type of job at a certain company can only join a single union if one is already recognised by their employer?!
> What, so in the US people doing a certain type of job at a certain company can only join a single union if one is already recognised by their employer?!
Yes.
There are a few exceptions, but by and large: once a union is granted authorization over a bargaining unit, the union exclusively represents all employees included in the bargaining unit (whether or not those employees voted for the union or are members of the union).
Unions usually do more than just bargain and organize, including setting up funds to buffer the members in the event of a work stoppage, and getting insurance benefits for the members.