Canada does not have exit immigration controls, so PR residence fraud is still an issue. An agreement with the US to share data on people leaving Canada via the US has been announced and re-announced, but hasn't been implemented yet. Which is all to say that if you land in Canada, drive over the border and then fly abroad, the immigration bureaucracy still has no idea you've ever left.
You would need a new passport for that to work, and it increases barriers to doing so.
In any large scale endeavor it's often about decreasing the number, changing the balanace vs. reducing it to zero. And it's often a ratchet, adding a law here and there to get to a result.
