What is the point of employer-based and government-based healthcare?

Explain something to me… Why does my government need to buy me health care? I want health care for myself – there is no issue of externalities to worry about, so it makes no economic sense. And I might want more or less or different healthcare coverage than my neighbor – so buying the same plan for everybody in the country makes no sense, because either you go all out, wasting money, or don’t go far at all, and most of the country has to buy real healthcare, or you go somewhere in the middle, half the country buys its own healthcare, and most of the country overpays, and nobody is happy. I don’t get why employers give healthcare, either – if they gave money instead, then households with more than one job among them can earn the added benefit from all of them, instead of having redundancy in their healthcare, wasting money. If every employer and the government all offer healthcare for the people, the redundancy is unavoidable, except by the homeless. So… How is government or employer sponsored healthcare a good idea? Why can’t people just buy the healthcare that suits them, privately, at a government-controlled and possibly government-subsidized rate?