As with a lot of things, such as vacation time, Americans seem to prefer to provide certain social goods as employer benefits because that way it seems more like a reward for competitive merit, which one can show off as a status symbol, than like a universal social good.
Maybe some psychos think of it that way, but no one I have ever met, at least not regarding insurance. Some fringe benefits like unlimited vacation, free lunch, etc, maybe I can agree.
Another way to see it is to ask why a company should be able to reap the labour benefits of their workers and then force other people to pay for their basic needs?