> any worker unions were against the lowering the taxes on paychecks (higher net with same gross pay),

Seems to be quite a lot of context missing. I think nearly everyone agrees they want to pay less taxes and take home more money. Now if lowering taxes does not result in more money then you don't need politicians and unions to make that case.

I'm guessing lowering taxes would result in more expensive, privatized services and voters figured that wouldn't work.