When building your home, you have the option of hiring non-union workers. Workers have the option of not joining the union. The union essentially acts as a service provider to the independent workers. These individuals charge quite a bit more than non-union workers, but often have astounding levels of competence, productivity, and workmanship.

When a company is unionized, none of those things are true. Instead of the union being a de facto endorsement of a particular worker, it acts to protect its own power over the workers. Instead of the company having a choice about who to hire for a particular role, it is forced into one choice. Instead of workers joining a union for their own benefit, they are forced to join because of legal coercion. The union is highly motivated to control and limit its members--freedom for the members means destruction of the union.