It's a simple matter of incentive. With government medicine, you are a cost unless you are still paying plenty of taxes - which is around only 10% of the population, or less. If you are sick or disabled, you become even more of a burden to "the common good."
With private insurance, they want you alive to pay your premium.
Anybody who believes in government benevolence is in dreamland: as we have been saying here, government is just another powerful special interest group. A doc's committment is quite the opposite.
And nobody wants their doctor worrying about "the common good."