I'd read that the way healthcare became tied to employment had less to do with some beneficent interpretation of the "social contract" than it did taxes.
That is, when the two were first tied, income tax rates (especially for higher, including "professional", brackets) were much higher. Employer-sponsored insurance was first offered as a tax-free perk companies could use to draw talent. It's easy to see how that could become an expectation, and then a requirement, despite its helping create incentives that are ultimately aligned against the employee/patient.
In 1943, the War Labor Board ruled that wage freezes due to WWII did not apply to fringe benefits, which included health insurance. So you couldn't pay your employees more money, but you could pay their health insurance.
That is, when the two were first tied, income tax rates (especially for higher, including "professional", brackets) were much higher. Employer-sponsored insurance was first offered as a tax-free perk companies could use to draw talent. It's easy to see how that could become an expectation, and then a requirement, despite its helping create incentives that are ultimately aligned against the employee/patient.