I'm not in a union, so I've always figured I'm on my own, that my boss can do whatever they want and I just have to take it. When something feels wrong at work I stay quiet, because I assume I have no rights and no backup. Maybe I do have some, but I honestly wouldn't know where to even find out.
More people experience this than they realize.
You assume no union means no protections, so you stay quiet.
If this sounds familiar, the Library can help you find the bigger picture.