Many people are against people getting something they didn't earn. And if you are union, and not free market, it most certainly wasn't all earned. It was gotten through nothing less than legalized extortion and strong arming.
And as a result, everybody else has to subsidize the union worker's grossly overpaid salaries through the higher costs of goods and services. And many don't even have jobs because of unions because more and more companies and just going overseas to avoid dealing with unions and having to pay the union people more than they are worth.
This is how it should work (and how it does work outside of unions). If you don't like your pay or benefits with one company, you go work for another company. If one company can't attract the talent they need, they will start paying more to get better talent. Companies will pay according to the value that you bring to them. It is called a free market, and everybody ends up getting paid what they are worth. I know you may not be happy with the amount you end up getting paid, but it still is all you are worth, all you deserve, and all that you have earned. To extort more than that is theft.
What if all companies that used electrical workers all got together and said from now on they will no longer pay above $15/hr, and would only offer X benefits, and anybody that doesn't like it is fired? And you have no choice because you need a job and it is the only skill you have so you are stuck because all the companies agreed to it amongst themselves and there is nothing you can do about it. Well companies aren't allowed to do that, and workers shouldn't be allowed to band together and use strong arm extortion either.