Isn't the idea to arrive at a salary that is fair to all parties? If you are good at negotiating, then perhaps you can be a voice for your workplace as a whole,

Isn't the idea to arrive at a salary that is fair to all parties? If you are good at negotiating, then perhaps you can be a voice for your workplace as a whole, instead of leaving the less gifted negotiators lacking. Even if you completely despise your co-workers, the idea and support for unions is about systematic worker influence rather that "everyone will get a raise".