Having a union doesn't mean you can't be fired. It means the company has to follow a process and have evidence of an infraction and the union will have your back as the process unfolds. Just as even a guilty person deserves representation in court, a union ensures an employee has representation in a dismissal process and can't be fired just on the whim of a manager who was having a bad day. Makes things more difficult for managers, but that's why they get paid the big bucks. Now, unions are human institutions, and can be just as scammy and scummy as any other (mmm, commercial corporations? churches?), but they do have value for workers beyond higher pay and better benefits (which is itself valuable of course).