A good union is meant to help the worker gain leverage in all thing related to their employer. Example, better wages, working conditions and better health insurance options. Not all unions are created equal. Some are not great and they’re only as good as the members involved.
The direct answer to your question can be summarized in one word. "representation." Unions represent the voice(s) of the employee(s). They advocate for you and help move forward your causes.
I was a union officer and debate for the state of Illinois. We marched in San Francisco for better wages, working conditions and for Director Wilke to finally honor our union contact. I always visit Capital Hill to discuss our issues with high census, dangerous staffing ratios, and Healthcare for all. If all you do is sign up your not helping you have to participate and fight for the change you want.
To extort money from workers for political gain. Sometimes the politics work in favor of the workers.
