> Health insurance is "tied to employment" because of wage controls that were implemented in WWII.

If that was the only or even dominant reason, then the removal of those controls in 1945 would have seen that tie rapidly unravel, instead, health care has become more, not less, tied to employment since the end of that policy, reinforced by deliberate policy choices like tax policy and explicit mandates.

The historical reason a thing first became common and the reason the thing is still common are often not all the same.