I didn't say the union was about minimum wage. I said it was about minimum wages. ie. What is the lowest you can pay a specific worker. For example, the actor's labor union has set the minimum pay at $750 a day. That's far more than the legal minimum wage, but it is the lowest a movie studio is allowed to pay an actor.

Therefore they have now negotiated the minimum wage for an actor. It's still higher than the legal minimum wage, but it's still a minimum wage. The studio would pay less if they could.

That's what unions are all about. Setting the minimum compensation for a particular worker.