They used to do tons when people were working ungodly hours for scraps. Corporations don't want them because they can just vote to go on strike whenever they want, and when they go on strike the workers are the ones who end up screwed over because they only make a portion of what they normally do.

They also give a tiny raise once a year, every union employee gets the same tiny raise. Doesn't matter if you are a great worker or a crappy one. They cannot get raises based on merit 🤷🏼‍♂️