The problem with traditional unions is that they reward seniority not accomplishment or level of contribution. No matter how motivated or energetic a union member, eventually they will get "union-member's disease" (not unlike short-timer's disease) in that kind of environment. Some unions have made an effort to use more than simple seniority in determining level of compensation, but so far they are pretty rare.

That's not to say that unions have not played an extremely important role in securing worker's rights since the industrial revolution, but as the workplace has changed, unions have not kept up and have lost relevance. They could be just as valuable today, but they need to catch up with the times or risk becoming completely irrelevant.