I just did.
In the majority of cases, if you are part of the union you can't back out and retain your job.
When a union forms, if you are part of the <50% who did not want to join, too bad in the majority of cases. Either you join or find a new job.
In my area, there are two major chain grocery stores. One is union, one is not. They have nearly identical benefit packages for their workers. Identical pay scales. Only difference is that the Union members see more money taken out of their check for union dues than the non-union store. For no extra benefits than the non-union store.
Yeah, thats a winner for the workers.

Lets take more money away from those who can least afford to lose it.