One thing to bear in mind is that the rights those members enjoy are relatively new and arose out of the formalization/legalization of the labour relations process over the past 5 or 6 decades. For most of our history, the role of unions was much more diffuse and much more political. Labour unions, not political parties, were the foundational institution of progressive politics.

Of course, now we do have parties that identify as ‘left,’ which some take to mean that unions no longer need to be involved in the broader political discourse. I’d argue that there currently is no proper social democratic (small-L) labour party with representation in the Canadian Parliament. That argument aside, however, we shouldn’t forget that the electoral arena is just that: an arena. Politics isn’t only done in one place, and capital has all sorts of well-financed representation in civil society. Unions are one of the only reasonably well-financed voices for working people.

And even if you reject all that, let’s not forget that even the narrow legal rights enjoyed by today’s workers are constantly under threat. Protecting those rights requires a political response.