I don't see why I would need a union to defend my rights. aren't there courts to decide who's right and who's wrong? you don't like how you're being trated, you just have to point out what laws your employer is breaking, right?
Courts don't decide right and wrong, they decide what is legal. While the government will protect you from flagrant offenses, they aren't going to get involved in every minor issue. They only need to make sure you get a minimum liveable wage and aren't discriminated against.
For example, teacher's unions, while far from perfect, are extremely necessary. Education is not an industry that has clear profit and gains. An inexperienced young teacher makes considerably less than a veteran teacher. School districts have no real reason to pay veteran teachers, they don't necessarily bring in more money to the school. So a Union is the only protection that they have.
Unions tend to be born out of necessity, so if the video game industry continues down this path, I wouldn't be surprised to see it happen.