Employers are presumably paying taxes, so funding it through taxes is not letting them off the hook. Additionally, what about people who are unemployed (which is now >20% by U6 in the US) or work in jobs that don't offer healthcare? And what if you get fired? Or you want to change jobs but have a health condition which means you'll be in trouble without health insurance? Or your employer changes health insurance providers without consulting you and now your coverage or doctor has changed? These aren't hypotheticals, they're the daily reality of millions of people in the US.
I don't understand this weirdly business-centric view that folks from the US have on the topic of healthcare. Surely a more productive view is that it is the best interests of society that we keep our fellow citizens as healthy as possible? Even ignoring the ethical arguments (which should be more than enough), healthy citizens make healthy workers and reduce long-term healthcare costs caused by preventable illnesses.
Health insurance shouldn't depend on work or the size of your employer, period. Not only should employers have healthy employees, but the applicants should be too.