They generally don't move back. Anyone who qualifies for Medicare (10 years of employment in the US) will get significantly higher quality healthcare through Medicare than they would receive in Canada.
The problem is that Canada's healthcare system is a command economy. The government decides how many med school spots there are, how many residency places, and how many procedures will be funded each year. In order to keep costs down this results in rationing. You can't even pay out of pocket - it is against the law for Canadians to purchase private care in Canada. The end result is that people with means end up going to the US, and everyone else waits 6-12 months for medically necessary hip or knee replacements. Even critical medical imaging is backed up weeks. I know someone who waited multiple weeks for urgent cancer screening. The same scans are available in the US in 24-48 hours, for a few hundred bucks.
The problem is that Canada's healthcare system is a command economy. The government decides how many med school spots there are, how many residency places, and how many procedures will be funded each year. In order to keep costs down this results in rationing. You can't even pay out of pocket - it is against the law for Canadians to purchase private care in Canada. The end result is that people with means end up going to the US, and everyone else waits 6-12 months for medically necessary hip or knee replacements. Even critical medical imaging is backed up weeks. I know someone who waited multiple weeks for urgent cancer screening. The same scans are available in the US in 24-48 hours, for a few hundred bucks.