Why, then, does Major League Baseball have a union? These are very high skilled jobs, very well paid. The highest performers make FAR more money than the middling ones - having a union doesn't prevent that.
My father spent most of his working life in union supermarkets in Los Angles, most of the time in management. Except when he was just starting out, he never worked for union scale, but negotiated a higher rate because he was known to be good enough to deserve it. No matter what the unions say, you can always get more if you can make the boss believe that you deserve it.