They can in some cases do, particularly in the US.
It's still a possibility.
edit: Fair points. I still believe that modern labor is a highly dynamical system. Many workers do need additional support and benefits, but our corner of the world is one of the best compensated and least regulated. Solutions for getting low-paid workers better equity shouldn't be used as a hammer -- workers earning six to seven figures do not need unions. Unions in tech will put downward pressure on our mobility, competitiveness, and compensation.
But you enjoy many of the benefits past union members fought and died for.
We owe a debt to those who worked to get us simple humane things like taking children out of coalmines and getting benefits for working beyond 40 hours per week. Those days are gone. Now they fight to keep people who get drunk on the job or try to tell our factories that some people should stand around and do nothing because asking them to help move some parts from one room to another isn’t in their narrowly defined job description.