Additionally, there's a not insubstantial chunk of Medicare spending that's essentially fraudulent, and that no "real" insurance company would pay, but Medicare

Additionally, there's a not insubstantial chunk of Medicare spending that's essentially fraudulent, and that no "real" insurance company would pay, but Medicare lacks the "overhead" to do much about all but the most egregious cases. Why else did you think there were so many daytime TV ads for "free" scooters before Medicare cracked down? And that's just one example.