alt Hacker NewsA key problem in the US is that in a unionized job you are legally required to be represented by the union. Union membership is non-voluntary.
If you think you are part of that top percentage or even if you think that the union is not representing your interests, tough luck. It is illegal to quit or reorganize like-minded individuals to form your own that better represents you. To reform the union you need to get 50% of the members to vote for change instead of just forming a new, smaller organization that represents your interests.
This is in contrast to many European unions where you can choose to join because you think they provide worthwhile benefits. Or you can choose to not join because it does not. Unions need to compete on benefits to their members and are thus incentivized to provide better benefits.
Also in the US, when Unions were starting to get going, the "good" ones that stood on principles and tried to do right by their members had their leadership harassed and even murdered by oligarchs and the government. The corruptible ones were allowed to exist, and be corrupted as another means of control, and for the anti-union people to point at as proof that unions "don't work".
Reading up on this has been eye-opening, they didn't teach much about it in school, except maybe a paragraph in the history textbook about the Ludlow Massacre. They don't mention at all the IWW or other leftist unions from the 1910s and 20s. If they mention the Taft–Hartley Act, they don't talk about how it targeted "communist" union leaders, and left "capitalist" unions alone.