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.
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?
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.