Well, one, because our federal government has a massive deficit. That would be the first and foremost reason.
If you were an individual with the relative finances of the US federal government, you wouldn't be buying everyone health care. You'd be filing for bankruptcy and hoping to god that the judge gives you a favorable payment plan.
There'll be a day when we've ruined our economy beyond repair, and taxing people who don't have jobs a greater amount won't bring in more money. U.S. will then default on its loans to foreign governments. Then we'll really be in the shit.
Both the R's and D's want to run us into the ground financially and make a fortune in their political careers along the way. D's want to at least give people some basic benefits, which is a good thing. The R's want to see the world go up in flames from missiles and war. Will mean the same thing when we're all broke and starving in 100-200 years.