CRA's, why don't we have a union?

I work for a large CRO currently and have worked for a couple other big ones in the past. The work life balance has never been what it should be. I'm curious, why don't we have a union? How do we start one? It seems like at every organization upper management (VPs and CEOs) don't seem to care when their CRAs complain at company hall meetings, and nothing changes. How do we activate our field for a better future together?