Earlier quoted context omitted.
Because there are thousands of Canadians every year that go bankrupt because of health care costs. Actually, there are. They go the US to get care that's not offered in Canada. The care here is about as good as former soviet bloc countries. If there was a chance that an illness such as cancer could kill me, I'd get out of Canada in a heartbeat and embrace poverty if it meant keeping my life.
It's just not true that large numbers of Canadians go to the US for healthcare. You need to supply evidence of this. The numbers are vanishingly small.
Well, compared to what?
The odds of having your private health insurance rescinded in the US is also very small -- but it's quite likely among people who suddenly rack up big health care costs.
Similarly, if you compare Canada-to-US medical tourists to the Canadian population, I'm sure it's amazingly tiny. But how does it compare to the people of means who have a medical procedure denied by the Canadian system?
(I don't fault Canada for denying care in some cases. Sometimes it's not worth it. But the Canadian system would be better if people were still allowed to top off the denied care with their own dollars and didn't need to leave the country to get it.)