The past had slaves too. The feudal arrangement of tenant farmers was only one system of labor. I don't think union bargaining was ever tied to specific advances in technology.

Sorry, I'm drawing a blank on much history of slaves in a extremely-low-technological society or how it was imposed or ended in those societies, could you provide some examples of what you're meaning exactly by bringing slavery up? Feudalism or other things happening in those centuries is well into the technological era.

Are you saying you can't think of examples from the past of the introduction of technology changing labor dynamics or organization? Say, mechanical agriculture?

The changes are hardly going to always be good - there's no determinism of "new technology means society will get 'better'". But they've often been periods of change, and such periods are when it's easier to influence the direction if you happen to care about the direction of the change.