They have. Over time, Unions have a played a pivotal role in that, and rightly so. They've now been shaped, and that legal protection isn't going anywhere.
Employees with union membership aren't a thorn in the side of employers in the way they were when are laws were archaic.
The point that started the discussion, essentially, was that Union membership on its own, would make an employer feel differently about an employee. That's nonsense in my experience.