[fleitz]

Because developers don't see any advantage in unionizing.

It's like asking why cats don't herd.

Also many of the issues that matter to you don't matter to developers, or aren't convincingly argued.

If you want developers to unionize the first step is consulting them on what changes they'd like to see and then creating an organization to effect those changes, treat the union like a lean startup creating an MVP and I bet you may have success.