If there is no Medicare, that's going to knock out a huge chunk of health care demand, and send doctors who currently take Medicare patients fighting for the same patients as those who have opted out. So you will have same supply of doctors chasing a significantly reduced demand for health care. For supply and demand to equalize, prices will have to fall significantly, causing many health practices to fold.
I am in no way advocating an end to medicare. All people on medicare need access to health care, that isn't even up for debate IMO. All I am saying is that there are a small amount of doctors, who for various reasons, opt out of taking medicare patients. Usually they are very small private practices.
I think there is room for these type of doctors in the health care industry. Also, above you mention it would be better to take a $500 medicare CT scan than not at all. But what if the COST is $750? The doctor ends up losing money on this.
My doctor would retire if he was forced to take medicare patients, the cost/benefit simply isn't there. He would probably have to hire an extra billing/coding specialist, forgo profitable appts, and he also mentioned something about a $200,000 computer system that could be mandated in the near future if something passes, not sure of the details.
The bottom line is medicare or not, patients can usually see a doctor in very short order. They may not be able to see any doctor, but wait times of months or years is what a Canadian in this thread pointed out too.
Of all the problems our health care system has, I just don't see why the fact that some doctors can legally opt out of seeing medicare patients is one of them.