Now in that scenario the worker has no power at all, even though it actually is as we all know today, a proven benefit to have resonable working hours for the company.
So if you have a union and all the workers can collectively go “we need to talk about work hours or we strike” you force through the policy that is ultimately beneficial to the company, even though management hates the idea of there being 6hours more per day that their wage slaves are not at the work benches.
Why would workers argue for fewer hours if it doesn’t end up costing the company net profits? Because they are humans, not machines, and not everything in this world boils down to pure profit driven motives.