Counter to what you see touted on this website, unions are not solely about securing additional material benefits for workers. They are and have always been about changing workplaces from top-down, authoritarian models to ones where workers have a say in their company’s work and overall direction. They’re about acknowledging that none of these structures function or accomplish anything without labor and shifting thei…
I’ve yet to see any rational or coherent defense of why these (or any) companies should function like democracies. Company X offers to pay me to do job Y. My two options, as I see it, are taking the job and doing Y, or refusing to do Y and therefore not taking the job. I don't understand the logic of "I'll take the job but then refuse to do Y", except if I assume ill-intent from the person taking the job.
The opposite side of your logic, is that if you assume good faith on the side of the job taker, then the want to do the job that they signed up for, and is willing to do what it takes to make sure they are able to do that job in a safe, efficient, and non-soul crushing manner.
In addition, conditions can change from the initial agreement of employment. Lots of stuff about workplace environments are not fully captured in job contracts, and are so subject to change. You don't need to assume bad-faith from a person to understand why the might want to have a say in how things change. After all, they agreed to a job under a certain set of implied environments.
Companies do not have to function like democracies. However, companies that try to harness the moral and ethical motivation of their workers should always be aware of how to keep company actions and goals sufficiently aligned with those of their workers to be able to tap into that extra motivation.