Yes, but after a while if it's not getting fixed I just quit! The pay differences are usually token - one of my earlier jobs this happened, and when I found out the other person was getting paid more than me I was super bothered!
Unions and collective bargaining at their best give the employees leverage for better pay and profit share. They do create bad incentives around making it hard to fire bad employees and making things slow.
Unionization doesn't remove this ability, you know.