Game industry veteran here. It's not surprising to me at all. Large dev studios don't want unions. They've been able to capitalize on an endless sea of starry eyed young devs willing to work 60+ hour weeks for months on end for half the salary they could make in other software fields until they get burned out, just so they can say they worked on the 10th sequel of a game they loved as a kid, or tell their friends 'I worked on this game you can download here!' and it doesn't look like the supply of that has gone down at all.
Meanwhile, individual software developers not in the midst of a company death march and are probably doing the Indie thing and tend to see themselves as lone wolves and thus don't make much effort to organize with their other developers.
There's associations like IGDA (International Game Developers Association), but in my interactions with them, I haven't seen them organize anything more than social activities with some veteran from the game industry to give a talk.