Unions are very important as they form a counterpart to the company's power.
OP asks the question of why not go to a lawyer but lawyers are expensive. In my country the losing party must pay the lawyer, so if you lose your argument, have fun paying a shitload of money for nothing.
Unions deal with issues that arise within a their own environment and tend to get better agreements than outsiders because they know who they deal with and they know the applied terms and conditions better.
Gameplay > Graphics
Substance > Style
Art Direction > Realism