It is an interesting question: why does Canada expect a permanent resident to live in Canada (although there are a few dispensations), while allowing a citizen (even where he/she was a former permanent resident) to live wherever he or she wants?
But those are the facts of the matter, and no amount of squabbling (as we see in this thread) will change this.
I believe that a person should have free rein to move to another country and reside there permanently -- as long as he/she will not become a financial drain on that new country. But that is my personal opinion, and is certainly not the view of other countries, who require me to get a visitor’s visa, or give me a visa at the border but require me to leave every 90 days, etc etc.
It is perhaps beyond the scope of this thread or even this forum, but I wonder whether we human beings are heading backwards to the days when inter-country travel was rare, as border controls get stiffer, and as travel becomes much more expensive because oil is running out.