Why do "progressives" feel state unions need Collective Bargaining when the Fed Unions haven't for 30+ years?

President Carter actually got rid of that abused privilege for all Federal Union members in the 1970s. If this was real issue (and not the actual issue progressive money and power being disrupted for the sake of the taxpayers and states they are bankrupting) wouldn't it make sense to repeal or even challenge the federal law first?