A union is much less likely to allow a company to use the cheapest health plan possible. So their purview is larger, as they need to ensure their members have access to basic benefits other countries provide “as right” regardless of union membership.

This means the cost, to the company, of using union labor is even higher, but also that more of the union’s money and energy is spent dealing with healthcare as opposed to ensuring safe workspaces or wage sharing or PTO or other labor concessions.