I think you made my point for me, at least partially.

The real teeth in a union is the ability to strike. In joining a union, you signify that you're willing to strike if enough other people aren't getting what they want.

I'm happy with what I have. My team seems pretty happy, too.

If things were bad, I'd consider joining a union. But until they are bad, union dues are just wasted money, and the obligation to strike if enough others want to.