It's odd to me that there would be a rights issue for some movies since most of them had worldwide releases. Would it not make sense to open up the content to everyone around the world so that there is no incentive to use a VPN service in the first place? Then again, businesses never do what makes sense.
What's going on in these situations is someone else already has purchased EXCLUSIVE rights to that content, so Netflix is simply unable to buy it.
So if Bell or Rogers has bought the exclusive Canadian rights to show a particular movie, then Netflix may have that title in the US, but not in Canada. The same thing happens in reverse too -- perhaps comcast owns the exclusive rights to broadcast a movie in the US but didn't purchase the Canadian rights -- in that case Netflix Canada will have a movie that the US Netflix doesn't. (Canadians complain about lacking the US content but we actually do get a bunch of content the US doesn't -- there is more on the US, but it's not a strict superset of what we have).
The problem here is the exclusive rights contracts -- at some level, they favour monopolies, and it would be better for all of us if copyright law somehow didn't allow exclusive rights contracts, or severely limited them to a short period of time, or some such (so, say, somebody could get an exclusive on a newly released title for a few months but after that everyone can run it). However, I suspect that would be hard to implement without trodding on somebody's constitutional rights somewhere.
At any rate, the reason why you can't see a movie on Canadian Netflix that is available in the US is because one of the big Canadian media monopolies bought an exclusive on it and isn't sharing.

