There are a lot of reasons why game workers need to organize, but it doesn't have to stop there. Tech workers in general can make the lives of their teammates a lot better by banding together.
We can also fight for the rights of others, why couldn't Amazon employees fight for the rights of Amazon's warehouse workers?
Also, things like discrimination and abuse are combated by organized workforces faster than they are by HR departments, especially when such abuse comes from managers. No individual worker is going to negotiate with a company on equal footing. It requires an organization of labor to do that.