It allows them some leverage over their constituents. For instance, in Michigan, a big union state, there is no state law mandating lunch or other breaks. That

It allows them some leverage over their constituents. For instance, in Michigan, a big union state, there is no state law mandating lunch or other breaks. That way, unions can say to employees, "Without a union, your employer can deny you a lunch or bathroom break." From a naive perspective, it has historically been ironically anti-union politicians who have backed worker protections, precisely because it takes ammunition away from unions. Why do you need a union if all the benefits are already written into law? Less union shops mean less union voters. But, to argue for the unions, not only do they negotiate wages, but also benefits. Maybe you aren't getting the minimum wage, but you might be getting better health care, a retirement account, overtime, paid vacation, sick time, flex time, etc. Whereas a non-union employer can say "We're paying a $15 minimum wage so we can't afford health insurance, vacation, etc." With a minimum wage, all you're guaranteed is that wage (other state laws aside).