What is theoretically stopping ED doctors from unionizing and getting a fair rate in major cities?

I want to work where I grew up.

However, jobs out there are low paying especially for the years of hard work (and debt and sacrifices) it takes to become an attending. After taxes I would be making less than a CRNA who sits on their ass all day and has no liability whatsoever.

Yes, I know I can make $350/hr in rural Texas but I won’t be happy there. Why do we, as ER doctors, not have the ability to negotiate our salaries as well as surgical specialists?

What if we all decide not to work unless our rate is at least $350/hr in metro cities. Wouldn’t hospitals have to pay up?